NATIONAL AERONAUTICS AND SPACE ADMINISTRATION The Deep Space Network Progress Report 42-25 November and December 1974 mac. },7L+ r^s p ort, NOV. ^' j. 7.. C-J L 173 t, 3/32 - °s JET PRO PULS CALIFORNIA INST PASADEN Eebri https://ntrs.nasa.gov/search.jsp?R=19750008624 2020-03-23T01:14:07+00:00Z Preface Beginning with Volume XX, the Deep Space Network Progress deport changed from the Technical Report 32- series to the Progress deport 42- series. The volume number continues the sequence of the preceding issues. Thus, Progress Report 42-20 is the twentieth volume of the Deep Space Network series, and is an uninter- rupted follow-on to Technical Report 32-1526, Volume XIX. This report presents USN progress in flight project support, tracking and data acquisition (TDA) research and technology, network engineering, hardware and software impleimentation, and operations. Each issue presents material in some, but not all. of the following categories in the order indicated: Description of the DSN -Iission Support Ongoing Planetary/Lntei'planetary Flight Projects Advanced Flight Projects Radio Science Radio Science Support Special Projects Supporting Rcseareb and Technology Tracking and Ground-Based Navigation Communications—Spacecraft/Ground Station Control and Operations Technology Network Control and Data Processing Network Engineering and Implementation Network Control System Ground Communications Deep Space Stations Operations Network Operations Nethvork Control System Operations Ground Communications Deep Space Stations Planning and Facilities T.DA Planning Facility Engineering In each issue, the part entitled "Description of the DSN" describes the functions and facilities of the DSN and may report the current configuration of one of the five DS.N systems (Tracking, Telemetry, Command, Monitor and Control, and Test and Training). The work described in this report series is either performed or managed by the Tracking and Data Acquisition organization of JPL for NASA. JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 iii Contents DESCRIPTION OF THE DSN DSN Functions and Facilities . . . . . . . . . . 1 N. A. Renzetti DSN Automatic Test Equipment Subsystem . . . . . . 5 C. M. Smith NASA Code 311-03.42.95 DSN Telemetry System .— Network Control Telemetry Subsystem 9 E. C. Gatz and R. R. Wynn NASA Code 311.03.42-94 DSN Wideband Data Subsystem . . . . . . . . . 13 C. K. Stein NASA Code 311-03.42.94 MISSION SUPPORT Ongoing Planetary/ Interplanetary Flight Projects Mariner 10 Mission Support . . . . . . . . . . . . . E. K. Davis NASA code 311.03-21-60 Viking Mission Support . . . . . . . . . . . . . . . 37 D. J. Mudgway NASA Code 311.03.21.70 31 Helios Mission Support . . . . . . . . . . . . . . . . 43 P. S. Goodwin NASA Code 311.03.21.50 SUPPORTING RESEARCH AND TECHNOLOGY Tracking and Ground-Based Navigation DSN=MVM'73 S/X Dual-Frequency Doppler Demonstration During Superior Conjunction . . . . . . . . . . . . K. W. Yip, F. B. Winn, and S. J. ReinbOid NASA Code 310.10.60.52 Non -ionizing Radiation Hazards With the High-Power X-Band Transmitter . . . . . . . . . . . . . . . . . R. B. Kolbly NASA Code 310-10.64.01 . . 47 . . 55 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 PIRWMING PAGE BLANK NOT MMW v Noisy Reference Effects on Multiple-Antenna Reception . . . . . . 60 J. W. Layland NASA Code 31.0.10.61-01 Communications-Spacecraft/Ground Low Noise Receivers: Microwave Maser Development . . . . . . . 65 R, C. Gauss NASA Code 31020.66.01 S/X Band Experiment: A Study of the Effects of Multipath on Two-Way Rangp . . . . . . . . . . . . . . . . . . 69 T. Y. Otoshi NASA Code 31020.66.06 Maximum Likelihood vs Threshold Frame Synchronization . . . . . 84 B. K. Levitt NASA Code 310.20.67.08 Further Applications of the Atmospheric Fading Model to Sequenti . Decoding Performance 88 B. K. Levitt NASA Code 310.20.67-08 A Multiple-Rate Command System . . . . . . . . . . 94 R. F. Emerson NASA Code 31020.67.09 Golay--Viterbi Decoding: Results of the MVM'73 X-Band Telemetry Experiment . . . . . . . . . . . . . . . . 108 L. D. Baumert and R. J. MeE_ liece NASA Code 310.20.67-08 A Signal Combiner for Antenna Arraying . . . . . . . . . . . 111 H. Wilck NASA Code 310.20.67.09 Station Control and Operations Technology DSN Research and Technology Support . . . . . . . . . . . 118 E. B. Jackson and A. L. Price NASA Code 310.30-69.02 Hybrid Integrated Circuit Development . . . . . . . . . . . 1.23 C. F. Foster NASA Code 310.30.68-10 Automated Pulsar Data Collector . . . . . . . . . . . . . 129 S. S. Brokl NASA Code 340-30.68-06 Y1 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 NETWORK ENGINEERING AND IMPLEMENTATION Ground Communications Automatic Total Recall Program for Replay of DSN 7-Track DODRs 137 F. M. Nlavaty NASA Code 311.03.42-53 OPERATIONS Network Operations A New Radio frequency Angular Tropospheric Refraction Model . . . . 142 A. L. Berman and S. T. Rockwell NASA Code 311.03.13-20 A New Approach to the Evaluation and Prediction of Wet Tropospheric Zenith Range Refraction . . . . . . . . . . . i54 A. L. Berman NASA Code 311.03.13.20 Doppler Phase-Noise Measurement Using Mean-Sweep Techniques 163 R. C. Bunee NASA Code 311-03.14.52 Bibliography 172 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 DSN Functions and Facilities N. A. Renzetti Office of Tracking and Data Acquisition The objectives, functions, and organization of the Deep Space Network are summarized. Deep space station, ground communication, and network operations control capabilities are described. • 'i 3 j ^l The Deep Space Network (DSN), established by the (4) Mariner Mars 1964. National Aeronautics and Space Administration (NASA) Office of Tracking and Data Acquisition (OTDA) under (5) Mariner Venus 1967. the system management and technical direction of the Jet Propulsion Laboratory (JPL), is designed for two -way (6) Mariner Mars 1969. communications -wlfli unmanned spacecraft traveling lip- i proximately 16;00( km the(10,000 mi) from Earth to t (7) Mariner Mars 1971. fartliest planets of citir solar syster.. It has provided track- (g) Mariner Venus/Mercury 1973. ing and data acquisition .support for the following NASA deep space exploration Projects, for wIhieh JPL has been responsible for the project management, development of The DSN has also provided tracking and data. acquisi- the spacecraft, and conduct of mission operations: tian support for the following projects: 1 Ranger. 1 Lunar. Orbiter, for which the Langley Research (2) Surveyor. Center carried out the project management, space-ti craft develrp^nent, and mission operations font- (3) Mariner Venus 1962. tions. i . 4: 4 JPL 'DEEP SPACE NETWORK PROGRESS REPORT 42.25 i ,, t?, Pioneer, for which the Ames Research C.'enter car- ried out the project management, spacecraft devel- opment, and mission operations functions. (3) Apollo, for which the Lyndon 11. Johnson Space Center was the project center and the Deep Splice Network supplemented the Spaceflight Tracking and Data Netwwork. (STIM which is rnanagt •il by the Coddard Space Flight Center (CSFC). (4) I IeIios, a joint United States/11'est Germany project. (5) Viking, for .which the Langley Research Center pro- vides (lie project management and Lander space- craft, and c ondttcts mission operations, and foi which }PI., provides the Orbiter spacecraft. The Deep Space Network is one of two NASA net- works. The other, the Spaceflight Tracking . and Data Network, is under the system management and technical direction of the Goddard Space Flight Center, Its f ►nretion is to support manned and unmanned Earth-orbiting and lunar scientific and advanced technology satellites. Al- though the 13SN was concerned with unmanned lunar spacecraft in its early years, its primary objective now and into the future is to continue its support of planetary and interplanetary flight projects. A development objective has been to keep the network capability at the state of the art of telecommunications and data handling and to support as many flight projects as possible with a minimum of mission-dependent hard- ware and software. The DSN provides direct support to each flight project through that prajec:t's track.-ing and data systems. This management element is responsible for the design and operation of the hardware and software in the DSN which are required for the conduct of flight operations. As of Jul)-1972, NASA undertook a change in the inter- face between the network and the flight projects. Since January 1, 1964., the network, in addition to consisting of the Deep Space Stations and the Ground Communications Facility, had also included the Nfission Control and Com- puting Facility and had provided the equipment in the mission support areas for the conduct of mission opera tions. The latter facilities were housed in a building at JPL known as the Space Flight Operations Facility (SFOF). The interface change was to accommodate a hardware interface between the network operations con- trol functions and the mission control and computing functions. This resulted in the fI.ight project's picking up the cognizance of the large general-purpose digital com- puters, .which were ttwd for network processing as well as mission data processing. It also assumed cognivance of all of the equipment in the flight operations facility for display and communications necessary for the conduct of mission operations. The network has already undertaken the development of hardware and computer software necessary to do its network operations control and monitor functions in separate computers, This activity became known as the Network Control System implementation. A characteristic of the new interface is that the network provides direct data flow to and from the stations via appropriate ground communications equipment to Mission Operations Centers, wherever they may be, namely, metric data, science and engineering telemetry, and such network monitor data as are useful to the flight project. It accepts command slats ► froth the flight project directly into the ground communications equipment for trans- mission to the station and thence to the spacecraft in a standardized format. In carrying out its functions, the network .,,;tivities can he dividers into two general areas. The first includes those functions which are associated with the in-flight support and in tracking the spacecraft, its configuration can be characterized as follows: (1) DSN Tracking System. Generates radio metric data; i.e., angles, once- and two-way doppler and range, and transmits raw data to Inission Control. (2) DSN Telemetry System. Receives, decodes, records, and retransmits engineering and scientific data generated in the spacecraft to Mission Control. (3) DSN Command System. Accepts coded signals from Mission Control via the Ground Communications Facility (GCF) and transmits them to the space- craft in order to initiate spacecraft functions in flight, The second category of activity supports testing, train- ing, and network operations control functions and is con- figured as follows: (1) DSN Monitor and Control System. Instruments, transmits, records, and displays those parameters of the DSN necessary to verify configuration and validate the network.. Provides operational direction and configuration control of the network and primary interface with flight project mission control personnel. h { f t (2) DSN Test anti Training System. Generates and con- trols simulated data to support development, test, training, and fault isolation within the DSN. Partici- pates in mission simulation with flight projects. The capabilities needed to carry out the above func- tions have evolved in three technical areas: (1) The Deep Space Stations that are distributed around Earth and which, prior to 1964, formed part of the Deep. Space Instrumentation Facility. The technology involved in egWpping these sta- tions is strongly related to the state of the art of telecommunications and flight/ground design con- siderations and is alnicnt completely multimission in character. Table 1 gives a. description of the Deep Space Stations and the Deep Space Communica- tions Complexes (DSCCs) they comprise. (2) Ground communications. This technology supports the Eartli-based pclint-to-point voice and data com- munications from the stations to the Network Operations Control Area at JPL,. Pasadena, and to the Mission Operations Centers, wherever they may be, It is based 'largely: on the capabilities of the common carriers throughout the world which are engineered into an integrated system by the Goddard Space Flight Center for support of all NASA programs, .The term "Cround Coznmun.ica-. tions Facility" is used for the sets of hardware and software needed to carry out the functions. The Network Operations Control. Center is the func- tioiial entity for centralized operational control .of the network ` and interfaces with the users. It has two separable functional element,; namely, Network Opera- tions Controland Network Data Processing. The functions of the Network Operations Control Cen- ter are ®r Control and coordination of network snpport to Ineet commitments to network iitier4. (2) Utilization of the network data processing coin- putinn capability to generate all standards and limits required for network operations. (3) Utilization of network data processing computing capability to analyze and validate the performance of till network systems. The personnel who carry out the above functions are on the first floor of Building 230, wherein mission operations functions are carried out b y certain flight projects. Net- work personnel are directed by an Operations Control Chief. The functions of the Network Data Processing are: (1). Processing of data used by Network Operatiows Control for the control and analysis of (lie network. (2) Display in Network Operations Control Area of data processed in Network Data Processing .Area. (3) Interface with communications circuits for input to and output from Network Data Processing Area. .(t) Data logging and production . of the intermediate data records. The personnel who Barry out these functions are ln- cated in Building 202, which .is approximately 200 .m from Building 230. The equipment consists of minicomputers for real-time data system monitoring, two XDS Sigma a's, display, magnetic tape recorders, and appropriate inter- face`equipment with the ground data communications, -a i 33 i '. 1 i 4 i 1. Table I. Tracking and data acquisition stations of the DSN a 5 Antenna DSS serial Year of initial DSCG Location 1]SS desigeiation Diameter, Type of operation m (ft) mounting a Goldstone California Pioneer l i 26(85) Polar 1958 Echo 12 2.6(85) Polar 1962 (Venus) 13 26(85) Az-E1 1962 i \Tars 14 64(210) Az-El 1966 d l 'ridbinbills. Australia.. 42 26(85) Polio 1965 liallinza 43 64(210) Az-El 1973 Australia I Ioncytiuckle Creek 44 26(85) X-Y 1973 Madrid Spain 1106ledo 61 26(85) Polar 1965 1 Cehreros 62 .26(85) Polar 1967 liohledo 63 64(2I0) Az-El 1973 "A maintenance facility. Besides the 26-m(85-ft ) diam Az-El mounted antenna, DSS 1'3 has a 9-m (30-ft) di. Az-Ei mounted antenna that is used for interstation time, correlation using:lunar Teflection techniques, for te_,ting the design of new equipment', and for support of ground-bused radio science. ;. w e' : S 4 JPt . DEEP ,SPACE NETWORK PROGRESS REPORT 42.25 k 7 Pr. v rrA DSN Automatic Test Equipment Subsystem C: M : Smith ^ _ DSN Systems Engineering Office C The Automatic Test Equipment ` 'Subsystern: (ATE) described in this article is being implemented to provide the capability to adequately test existing. and future modules to existing and future- test criteria. The initial ATE will be implemented at the Deep Space Network (DSN) Maintenance Center (DMC), providing di. ital test ca ab li nr a cross section o DSN modules. A nai:A:TEp g g ' p ty f f fi. pvaviding complete network support will be implemented at the DMC and all . Complex Maintenance Facilities. This article presents a description of the ATE design. and.implementation.... 1. Introduction 11. Implementation ..For: quite soine'time, there has been>an unmistakable A . computerized . test subsystem in . response to . the .: 2 trend toward the use of medium- and large-scale objectives of the DSN must be capable of change to meet r: integrated circuits, hybrids, thick 'Mms,. and other types' of the dynamic' requirements described above and must also : estminiaturized large-scale arrays. Presentt criteria and be compatible with present economic and practical r practices have 'beeume inadequate . :to cope. with the . constraints. A our-p implementation plan has been',. complexity and miniaturization—not only in degree, but developed: y also in kind I rov'des the DSN(I} Phase p. ^. Maintenance Center- The .increasin pin and. function'.densit '.of new rutted.g P Y P (DMC) with a single. automated dEgital. test. station: -, circuit modules (brought about largely because of large- ,^ 8 y g and an automated test program generator station. scale integration) requires a greatly increased size of test pattern, along with. increasing speed The test problems, (2} Phase lI .provides . each Complex Maintenance described herein, reveal the need fora . etieral.= ose Facility CMF ' with an automated digital, test '.>I P^ tY { Automatic Test Equipment Subsystem (ATE). station. . JPL DEEP SPACE NETWORK PROGRESS REPORT 42:2E 5 s (3) Phase III provides the DMC with an automated analog test station. (4) Phase IV provides each CMF with an automated analog test station. The DSN will generate the functional and detailed technical requirements. The actual development will be done by a contractor. Ill. Functional Description The Deep Space Network Automatic Test Equipment Subsystem is composed of hardware, software,. and maintenance personnel to provide on-line test and repair of DSN modules. The subsystem assembly functions and data flow are shown in Fig. 1. The ATE is totally modular in . nature,. and performs the following three main functions: (1) Dynamic testing. (2) Diagnostic testing. (3) Fault finding. The basic requirements developed for the DSN ATE hardware are: (1) The peripheral devices shall be capable of operating under computer control, and have a 32-bit word (serial and parallel) handling capability. (2) The 'hardware interface between peripheral device and computer input/output . (1/O) bus shall contain control logic which covers virtually every possible combination of logic required for all types of testing. (3) The data switching employed shall allow subsystem stimulus and measurement devices to be applied to any pin or combination of pins on the unit under test.. It shall be possible to simultaneously apply all such stimulus and measurement devices (whether analog or digital, or any combination thereof) to the unit under test. (4). Although. there is a large number of minicomputers available, a tradeoff analysis will be performed by the vendor, and at this time he will be aware of the DSN current and future requirements. Some of the basic requirements are as follows: (a)- Test program entry shall be via cassette tape. (b) Controlled transfers shall be rovided to andA. Key CharaderistiCS from up to BO peripheral devices. and. on The key characteristics of the ATE are as follows: expandable priority interrupt system. (1) Because of the .present availability of a wide variety (c) Word size: 16 bit; memory; 64K bytes; mass W .: of programmable peripheral devices, 90% of ATE storage: 5M bytes: hardware will be commercial off-the-shelf equip (d) Indirect addressing with up to N levels . ofmerit. nesting.- (2) The test software will be test-oriented, English-like (e) Instructions to permit control of memory protecprogramming language. tion or lockout: (3) 95% of all peripherals are programmable. (f) 'Direct addressing of entire memory. (4) Subsystem permits on-line generation and editing of ( Hardware-assisted environment switching.test programs...... (5) Hard-copies of test, results in a variety of. formats. A(h) utomatic traps for detection of error conditions. (fl) Comprehensive, evaluation of test results to obtain (i) Suffered input and output for communication diagnostic information, with external devices; once initiated, such 1/0. may continue without requiring further action by ;;a :. the computer. B. Hardware Analysis of the-existing peripheral: devices :indicated that C. Test Softwaremany problems associated with automatic test systems .. control (sequencing, timing, and housekeeping) are due The programming language' must be oriented toward mainly to standardization of these devices not having been the unit under test (UUT), rather than toward the test realized: Other problems associated' with programmable: subsystem itself : (with which : the programmer never . peripheral devices were identified, and it soon lircame addresses a device in the test subsystem, but only evident that the workings of these devices had to be describes the test to be performed on the UUT). With carefully examined and specified. a language, the user works only with a total 5 JPt. BEEP SPACE NETWORK PROGRESS REPORT 42-25 awl. r. subsystem. He neither knows nor cares that he has a programmable pulse generator from one manufacturer and. a pulse analyzer from another. Since the DSN ATE will utilize a UUT-oriented language, the user need not have a detailed knowledge of the test subsystem. (The user need know only his own UUT.) Some of the test language characteristics are as follows: (1) One-to-one correspondence between statements of the test language and .test functions. . (2) Statement formats may be fixed field. However, ease of use is a prime requirement. (3) The test operator shall have the capability, via the operator's console, to define or alter test functions and parameters. IV. Summary Advances in technology have brought about the need and, subsequently, the existence of several commercially available general-purpose automatic test systems. The DSN need to look beyond current test problems has been realized, resulting in the implementation of the Automatic Test Equipment Subsystem described in this report. 3 DISPLAY ASSEMBLY PROVIDES VISUAL DISPLAY OF CONTROL CONTENT PROVIDES PROGRAM EDITING VIA MAN/MACHINE INTERFACE PROVIDES OUTPUT CONTROL ....... .. . . CONTROL ASSEMBLY PROVIDES MASS STORAGE PROVIDES ON-LINE PROGRAM GENERATION PROVIDES SUBSYSTEM SOFTWARE/ HARDWARE MA NAGEMENT PROVIDES. DIAGNOSTICS, UTILITIES, AND MATH LIBRARY PROVIDES SUBSYSTEM SELF-TEST CAPABILITY PROVIDES CONFLICT RESOLUTION MEASUREMENT ASSEMBLY PERFORMS UNIT UNDER TEST DATA ANALYSIS PERFORMS FAULT ISOLATION VIA MAN/MACHINE INTERFACE PROVIDES PROGRAMMABLE VOLTAGE MONITORING i i k rl i 6 3 r- } DSN Telemetry System-Network Control - Telemetry Subsystem ` y E. C. Gatz and R. R. Wynn jl DSN Systems. Engineering. Office This article describes the real-time cathode ray tube displays which are now i generated in the Network Operations Control Center. These displays are derived from received telemetry data and give a continuous update on the status of the DSN Telemetry System and the detailed parameters for any selected stream.. 1. Introduction equipped with 64K words of memory, two disk drives, two . i A seal-time monitoring- capability. has been imple- cathode ray tube (CRT)/keyboard terminals, and one mented into the. 'DS1►1: Telemetry .System to allow keyboard character printer terminal. Additional CRT controllers and 'analysts to monitor the performance of displays are slaved to fire two . CRT/keyboard unitsi The: telemetry receiving and processing equipment in the terminal and display equipment is located in the Network Deep Space Network. This real-time monitor is part of Operations Control Area for use by network controllers the Network Control Telemetry Subsystem and is and analysts• implemented as part of the Network Control System Project. The processor can handle and display data from up to eight telemetry streams simultaneously. The presence of 4. The monitoring. is performed.. by . a: :MODCOMP II additional streams is indicated; the operator can select or F computer, located in the .basement of Building AM at n'L, delete the additional streams as desired. Two displays: are .z Pasadena: This computer is connected via'a Star Switch generated: telemetry status and telemetry analysis. The Controller to the Network Communications Processor. All content and format are described below.. Data for these telemetry high-speed _ data blocks : are routed.. to the two formats are.generated automatically and continuously, :. Telemetry Processor. The subsystem thus provides Either' can be called: on any CRT device. by the monitoring of all 'telemetry data sent from any ^P o rRtor. The :operator cats make appropriate keyboard Y1^ F Space Station to the Mission Control Center via high: entries to control the displays. Each. display is updated- :. speed: data :lines. The MODCOMP 11 computer. is every IU seconds.. °JPL'DEEP SPACE NETWORK: PROGRESS -REPORT 4225 9 - t11. Telemetry Status Display (3) MISG DATA indicates. that some data (at least one block) were missed. If the data are no longer being The telemetry status display format is shown in Fig. 1` received for this stream, the alarm will persist. If,A line is devoted tee t :!ach telemetry stream. Each stream is however, there is merely a gap, as indicated by uniquely defined by th° first five columns of the display: block sequence numbers and time tags, the alarm . DSS: Deep Space Station, will be removed when the data resume. SC: . Spacecraft number. (4) DELETED indicates that the row has been deleted by operator input. This alarm. persists until the row. .UDT: User data t number, identifies telemetry dataYl7e is released or reassigned by a subsequent operator3 and processor. input. 4 ' . DDT: Data-dependent type number, identifies telemetry .(5) OTHERS appears in row 10 only and indicates that ^ channel number and bit rate range. one and possibly several streams of data are being GDD: Gross data descriptor, identifies data as real-.time or received but not processed if the DSS through GDD playba: ik from tape. fields are filled. If they are blank, no other streams are being received. Up to eight lines are accommodated on the display. If more streams are present, the identifiers are displayed in turn on the tenth line with the indicator OTHERS. if the . operator is interested in one of these, he .can. delete a 111. Telemetry Analysis Display currently displayed stream to make: room for it.Y The telemetry analysis display format is shown in Fig. 2, -v For each stream displayed, the general status is Thisdisplay contains data related to a single stream. Any displayed in the next three columns: of the streams on the status display can be selected. Thedata are derived or extracted from ..the high -speed data SYNC: Status of frame sync. This is the result of blocks. The fields are .described as Rillows: processing to assure the quality of the data stream by (1) DDD : HHrMMiSS (FMT): The time (GMT) theverifying the frame sync. This indicator has four states: display was formatted. (1) Slash (/) indicates successful sync ` is achieved and` (2) DDD:HH;MM . SS: (DATA): The time (GMT) of themaintained block Rom which the data below are determined. (2) Asterisk (*} indicates failure to sync. (3) DSS through . GDD: The stream identifiers defined in (3) Blank indicates no data have yet been received. the status display. (4) Zero (0) indicates that the frame sync algorithm is (4) FSIZE: The frame .size in bits. . not active, either because it has been deleted by the (S) TIME TAG ERROR: The time tag error count, i.e., : operator or because data have sto PPS the number of time tag errors that have occurred COUNT: This is the count. of frames . that have been since the stream was assigned. This can be reset to received since sync was most recently acquired. When zero by operator input frame sync is lost,: the count remains unchanged;, when (g) PN ERR: Pseudonoise (PN) frame sync . errors 3 sync is reacquired; the count is restarted at zero. TheYn allowed indicate the number of bit errors allowed size of the count, therefore, indicates to the operator for sync acquisition and maintenance. the general stability and quality of the data stream. - - frame(7) FR SYNC:.. Indicates the .state of the sync s ' ALARM: The alarm field:has five possible values:p .: process. (1) Slash (/) indicates there are no time tag errors or (a) Slash.{/}. indicates in sync. data outages for the indicated stream (b) Asterisk (*) indicates - out of sync. (2) TIME MIR indicates that the difference between - the time tags on consecutive data blocks is not (c) Zero indicates that the processor is :not attempt f within 9% of the expected interval and cannot be ing to sync on the data (see the telemetry status . .. explained by Ehe :block - sequence numbers. The fia . format description),{ indicates a :faulty time tag and is maintained for at (d) Blank indicates that not. enough data have leer least one ,display update (10 seconds). received to make any sync determination. JPE DEEP .SPACE' !NETWORK PROGREft . REPORT 4225 ff i (8) FR COUNT: The number of frames since sync was List acquired. (9) RX: The receiver number and status (slash Is in lock, asterisk is out of lock). (10) SDA: The Subcarrier . Demodulator Assembly (SDA) is similar to the receiver indication. (11) SSA: The Symbol Synchronizer Assembly (SSA) fields may be a number and lock status, NA if not applicable or double asterisk (**). if an invalid number is received. (12) SDA: The Block Decoder Assembly (BDA) is OFF, or ON with status (slash or asterisk for in . or out of lock). (13) DDA: The Data Decoder Assembly (DDA) is similar to the SSA. (14) BIT SYNC: Bit sync is OFF or INT with kick :status:. (15) TCP: The number of the Telemetry Command. Processor (TCP) in use as 1, 2, or 3 or asterisk (*) if a.n invalid number is received: (16) AGC and SNR: Both the Automatic Gain Control (ACG) and Signal-to-Noise Ratio (SNR) are extracted directly from the data block and displayed in decimal format. The AGC has a negative sign and the SNR can have either a positive or negative sign. (11) BITRATE. The bit rate is deduced from the DDT and S/C. Fields 1,.-20 relate to data extracted from the telemetry frame. The selection is made by operator input. (18) DN LOG.- The data number location (DN LOC) is the location in Bits from the start of the sync code to . the beginning of the extracted data. (19) DN LGTH: The length in bits of the extracted data. Up to 33 bits may be selected: (20) DN: The data number in octal representation of the extracted data. m CL Irrsm Ind ^ o I' d 0 Cl S L C A 2 1 O In A, I = . 4 I, A ll ^ ^ l l ^ kt s i.. ^ rr 1 l lr L` jj I L•. ' ^I I - ^ . 4 r. 1: , fr i- 1 !E " . } .t ^ >. ^^ L 1 ^ : , : j rl^ ^ ti } 5ti s3 '^ is. ^ - - ."i','• f ^ - 1 { :s ck. l , r }} ,L I I } i J' i ,ira .F [.r.' ::] I+^ 1-1 #FF. ', ^. - ^ € - r•. ^ • 14 1 siy . : I l^ ^ '' 1 1^ 1 + J 1.1 {C !.f J V L rY I 3 ^ r 1 I [ I 7 !1 >+ : i ^ ' ^ {.I _ i 1 1 i 3 ' I+ F' " :1 }1- 'r . k,t - ' !, a L.+ .1 1 1: }. ;.1 4 :4 , , Z L 1 4 4 , ttt i,i ^ . L^ _ ,1 1K u ! _ ^ ,1 1 +1j i 4 1 ^ti ' I _ , f } i' , t € ri ^ 1 . 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R 1 ^1 ^ } t ^ Ji .I ` - sA `r i } } ) 7 ,^ i - 1 6 1.1 .d r' i. iil Irp y 3 1 f :I 1 Ilr I } 1 S' YY Y i^ ^L li L ^ xs . f - 4 4 1 i ^ I , Ie i ^ 1 t ::}: (I . :^.t {I` s1 ^ I, 11 ^ i. , ', ^ I il, r:l rk ts e's rk + lYx ^ 1r in Ja i..+ •y ^ 1 1 + [^S3 +i- : - - ^ 1.+ 1, l 4 1 4 ; 1 1 4 1 j p > ii: r n ^ :^ I ^I< ^^ . q i I te• 1 i JY f u r 1i 1 k[ - : 11 . ^ 1 1.k •l d } 1+ / 1 M1:l r4 I It L I - t :}+• tz ^ M lle ?^ it ` i .. ^ :^ ): I s. F } I ' r 1 tl i.{ ^ t - i^j ru 1 . _ : ri i' r c _ Y^ Y. 3 DSN Wideband Data Subsystem C. K. Stein Q5N Systems Engineering r x This article describes the Wideband Data Subsystem (WBS) of the Ground Communications Facility (GCF), which greatly increased the data .yield and. a t provided near-real-time video pictures during the Mariner 14 jl yby of the planets - Venus and Mercury. 3 I. Introduction pictures of the Mercury encounter were displayed. on 'a ,. large screen in near-real-time at both JPL and NASA A. General Headquarters in Washington, D. C. } ` When Columbus discovered America; .Queen Isabella B. Dap Space Network Descriptionhad to await his return to learn where he had gone. and what he had found. Even though our spaceships travel far To discuss, the wideband data link we must first H greater, distances than did Columbus' ships, we can almost understand how it fits.into the total picture of tracking and instantaneously obtain the kind of information from them data acquisition. The tracking and : data acquisition system A that " Isabella had to wait months for. The current state of for communicating with spacecraft beyond the moon the art of deep space exploration does not provide for the (Earth to the moon is referred to as near -space) is the return. .. of . an .exploratory vehicle; . therefore.., we must. DSN..The' DSN, communicates with spacecraft from Deep depend upon communication with it to obtain its scientific Space Station (DSS) locations on Earth approximately 12U }:. and engineering data. deg apart in longitude, two in north and one in south latitudes. These complexes are located near Madrid, Spain, Theof this article is .to review the Dee SpacepurPo p , _ Canberra, Australia, and Goldstone, California. The Network . (DSN) Wideband Data Subsystem (WBS) of the . general DSN configuration ;s shown in Fig: i. Ground Communication Facility (GCIi) that enabled us to r greatly increase the data yield and provide near-real-time The Network presently consists of one 64-meter video :(TV) pictures during the Mariner 10 flyby of the _ acantenna subset and two 26-meter antenna subnets. Eh. . Y planets Venus and Mercury. Although much information subnet includes` three .. antennas, one at each . location.. was gained by the video pictures from the cloud -shrouded These installations are known as Deep Space Stations. The Venus, the spectacular video mapping of the planet spacecraft data are transmitted and received via the Mercury was made possible by the :increased ' data rate_ TV.. antennas: at the D$Ss and Processed and sent yta -,, - JPL DEEP SPIKE NETWORK PROGRESS REPORT 42 .25 - 13 r.. telecommunication systems to JPL in Pasadena for (6) Full demultiplexing at DSS and Central Communica- processing and dissemination as specified by the mission tions Terminal to provide only requested data to plans. The facilities at JPL provide necessary data to the each user. DSSs for tracking and commanding the spacecraft by thereverse procedure: (7) Provision of subsystem real-time status . to GCF Monitor and Control Subsystem (manual during Mariner Venus/Mervary 1973). C. Ground Communications Facility (8) Project remote terminal equipment not supplied by Communications between JPL and the DSSs is accom- GCF' plished through the GCF. The 1973-1974 routing of the (9) Nonstandard (open) formats may be used on project interconnecting GCF network is shown in Fig. 2. The total circuits, but such circuits are not automatically communications system consists of combinations of series monitored nor will errors be detected by GCF. and parallel routings using communication satellites, microwaves, landlines, underwater (submarine) cables and (10) detect error polynomial provides positive error radio for redundancy and reliability. NASA Communica- - 'detection., tions (NASCOM) leases the long-Line.links and data sets (l1) :Block synchronous data transmission. and provides switching at Goddard Spare Flight Center (12) Receive timing provided continuously.(GSFC) Greenbelt, Maryland, and other locations as noted in Fig. 2. Although it is used primarily for the 64-meter subnet, the WBS can support one 26-meter antenna. station at Australia and one 26-meter antenna station at Spain because of a design commonality. 'Permanent wideband t!. Wideband Data Subsystem terminal equipment is installed at Australia and Spain, but .the :circuits are activated only when required .to support a A. General mission and its associated testing. There is permanent The Wideband Data Subsystem is primarily imple- wideband interconnection from JPL to Goldstone via a merited in the 64-meter (210-ft) antenna subnet: Figure .3 leased microwave link. This basic capability operates at is a simplified block diagram of this subsystem. It includes 28.5 kbps.. It will be upgraded. to: 50 kbps to support :the lines to the Compatibility Test Area at JPL (CTA 21) and Viking program in the 1976-1977 era. Redundant 230- the Spacecraft Compatibility/Monitor Station at Merritt kbps microwave super group circuits ware installed to Island (STDN MEQ.: these were included on the :block DSS 14 only to accommodate the Mariner 10 Venus and diagram because of their use in testing the WBS with the Mercury encounters, enabling the spacecraft to transmit spacecraft and will not be discussed further. NASCOM data at 117.6 kbps during the :critical. encounter time GSFC is the NAbA switching center at the Goddard Space periods A TV circuit was leased to transmit the near--real- Flight Center in Greenbelt, Maryland, and FDX indicates time video picture of the Mercury encounter from JPL, full duplex system (also denoted by double-arrowed lines). Pasadena, to NASA Headquarters in.Washington, D.C. 6 i The key design. characteristics of the DSN GCF Additionally, two 230-kbp3 super group wideband Wideband Subsystem are: i itcrcus we permanently activated from the PLill b lm:.. Y J:. Central Communication. Terminal . to the Network Opera- s (1). Permanent terminal . equipment with circuits acti- lions Control Center. Currently; 50-kbps wideband vated only when wideband data rates are needed, circuits are being used. thus reducing tease costs.. (2) Transmission rates of 28.5 and 50 kilobits per second As a :result of the . expansion of the, WBS a : cooled . (kbps) with bit error rates of 5 x 10-5 or better. multi lexer/demulti lexer (CMD) assembly s used to accomplish the equivalent functions of a block detection (3) .Standard,.120x/24(10-bit block format with better decoder and block demultiplexer. This device is smaller than 97% of all blocks delivered error-free in real and less. costly than the previously used individual units ,(4) time• and can operate at the rate of 250 kbps and higher, (4) Transmission error detection for all DSS circuits but accommodating block lengths of 1200, 2400 and 48M bits: no error correction. - Figure. 4 provides' a more detailed :diagram of the i l 4 (5) Rapid semi-automatic recall. -.. Wideband Subsystem being used during the Mariner 10 e 14 JOL . EiEEP SPACENETWORK PROGRESS . REPORT 4225 : i 1 i a F i mission. Redundant lines and/or switches are provided as expected to be 6 x 10- or better measured on a long- required to assure that the data can be received in real term basis. time. B. 28.5•kbps: Wideband Capability The basic, wideband data capability for the operation of the Deep Space Network during MVM'73 is 28.5 kbps. All .. equipment is permanently . installed In the .network... The Goldstone-JPL microwave link and the hard-wired circuits to the Compatibility Test Area (CTA 21) at JPL are permanently maintained. The circuits between the overseas stations and JPL are activated as required a sufficient time prior to the mission for the support of testing and are maintained throughout the mission. The WBS utilizes the present standard DSN 1200 bit-blocked data while the Mariner 10 project support data transmis- sions utilize a non-blocked word-formatted data transmis- sion mode. For wideband terminal equipment configura- tions refer to Figs. 5-7. C. 50-kbps Wideband Capability The 50-kbps wideband data rate is a requirement for future deep space missions. Initially, it is planned for support of the Viking program during orbit and dander operations in 1978 . and for the Mariner Jupiter/Saturn mission commencing in I97`! at the overseas stations only, since Goldstone GCF super group will be operating at 230 kbps for Mariner Jupiter/Saturn. During 1971, a lengthy wideband. data test was conducted between JPL and the NASCOM Madrid Switching Center in Spain. The purpose of this test was to determine if the error rates of. a circuit are generally comparable to those which were expected for the 28.5- kbps circuits planned for Mariner 10 support and to determine..the statistical distribution of the errors. 'Ile test was successful and the data satisfied both purposes. The configuration of the circuit used during this test is shown in Fig...8..A circuit (GW-5$819) was .provided by NASCOM and consisted of 303 C data sets operating at 50 kbps. The routing of this American Telephone and Telegraph circuit was not known nor were facilities from which. it was derived. The 303 :C data set. required substantially all of the 48-kHz passband; hence a group bandwidth was used. The routing overseas was via F communication satellite. as shown in Fig.. S. Test data consisted of 2047-bit pseudorandom bit pattern generated by Fredrich Electronic Company Model 600 test sets. At each receive location the pseudorandom ' € pattern wasalso .synchronized and compared . against .the test sets. The tests indicated that the bit error rate rnav be 0. 230-kbps Wideband Subsystem, Mariner 10 The CCF 230-kbps wideband capability during the Mariner 10 project consists of one full duplex ,super group transmission path from DSS 14 (64-meter station at Goldstone) to the JPL Central. Communication Terminal (CCT), then to the project computer interface. This wideband channel supported the real-time transmission of the Mariner 10, 117.6-kbps, high-rate telemetry data. The telemetry . data . were transmitted in a non-blocked, word- formatted mode and no specific GCF monitoring was provided. The GCF wideband super group capability was provided over existing 8-MHz radio channels of the DSS to the complex switching center (CCF 10), then via a.:230- kHz super group wideband channel between Goldstone and JPL over Western Union leased microwave equip- ment. This capability was provided from July 1973 through April 1974 for the Venus and. Mercury encounters and during August and September 1974 for the second Mercury encounter. Figures 9-11 illustrate this configura- tion from the incoming kbps signal through: (1) Project symbol synchronizer assembly (SSA) word formatter switch. (2) Project word formatter/deformatter. (3) Wideband digital patch panel. . (4) General Electric TDM-522 data set MODEM (digital-to-analog converter and data regenerator). (5) Wideband audio patch panels at DSS. (B} Wideband analog patch panel (Goldstone Comm Terminal). (7) General Electric TDM-501 data set; (8) General Electric TDM-520 data MODEM. (9) Western Union leased full duplex microwave between Goldstone and JPL.. (10) General Electric TDM'-520 data MODEM. (11) General Electric TDM-501 data set. (12)` DC patch panel: (13) Patch panels and cables. (14) Project word formatter/deformatter. The GCF 230-kbps system experienced almost no technical or installation problems and performance exceeded all expectations, The bit error rate was egv:al to I x 104 or better for a 99% throughput during the `srenus and Mercury encounters. ^ t L NeWA+ Operations Control Center Widaband Data Unk The Network Operations . Control Center (NOCC) is being implemented. in three .stages. All configurations include a wideband data link from the JPL Central Communications Terminal (CCT) to the data processing i equipment in the Network Data Processing Area. These i locations are in different buildings approximately OW meters apart. Figure 12 is a block diagram of the 50-kbps wideband system presently in operation. The system will be upgraded to.a 230-kbps super group during the 1975- r 1978 time period. is The NOCC receives data by tying into the. prime line between the DSSs and the project processing equipment. Two PDP-8 computers are located in the Network Data Processing Terminal adjacent to the GCF Communica- tions Terminal at JPL.. One of the PDP -$'s is prune, Inbound data undergo serial-to-byte transformation in an external . receive communications buffer. High -speed and wideband data are routed to the receive communications buffer and then .buffered in the PDP-8 to await multiples-. ing onto the 50-kbps wideband circuit. Filler blocks are high-speed block multiplexed onto the wideband line. Outbound data are routed essentially the .reverse sf inbound. The detailed block diagrams of both the Block I NDPT configuration and the Block I NDPA configuration are shown in Figs. 13 and 14, respectively. The PDP-8 and the Sigma-5 are interconnected .by General Electric 401 data. sets at either end of the wideband data lines. III. Conclusions The GCF Wideband Data Subsystem used in the Deep Space Network is unique in that it is wholly dedicated to transmitting data received by a ground antenna from a spacecraft and providing these data to theprocessing computers at JPL In real-time with very high reliability. Terminals are provided as permanent installations and lines to overseas stations are leased when required to support specific missions.. A variety of data sets, modems, converters, switches, switching centers, test equipment, jack panels and ancillary equipment , are provided. A follow-up paper would be useful to describe this equipment in detail, including inputs, outputs, functions and theory of operations; .however, these details are not a i a y r rejected rather than multiplexed. After multiplexing. the part of this report:high-speed and/or wideband blocks are placed in a second buffer to be clocked out to the wideband. data line to .the Even though . the Wddeband Data Subsystem . :is unique Network Data Processing Area (NDPA). External to the in that it is fully committed to the DSN, it is similar to PDP-8, byte-to-serial conversion occurs and, as required commercial systems in treat the blocks are formatted and by the wideband data lines, a voltage -to-current conver- addressed so that each block or series of blocks has an 3 sign .occurs. Multiple :high-speed data lines are thus originating location and. destination: The theory is buffered onto a synchronous circuit. To accommodate this compatible with the commercial packet packaging operation, the PDP-8 generates :a control message for the concept if one considers that data can be directed to r NDPA computer (Xerox Sigma-5) which precedes each various locations. i ` DSN FLIGHT PROJECT RADIO METRIC AND TELEMETRY DATA ' DEEP COMMAND AND MISSION MISSION SPACE GROUND SIMULATION DATA CONTROL STATIONS COMMUNICATIONS DSN MONITOR AND (LOCAL ANDCONTROL DATA REMOTE? f. MISSION. INFORMATION FOR REAL-TIME VALIDATION OF NETWORK CONFIGURATION AND OPERATIONS PERFORMANCE CONTROL NO ALTERATION CR DELAY OF INBOUND OR OIITBr',JND. DATA BY VALIDATION TECHNIQUE. SHARE OUTP_IUND DATA NETWORK DSN STATUS LINE WITH PROJECT CONTROL DATA EXTRACTS NEAR-REAL TIME REPORTING OF DSN STATUS TO MESS ION FROM GC LOG CONTROL '- CLOSE LIAISON WITH MISSION OPERATIONS TO :MINIMIZE DOWNTIME IN LOCATING AND CORRECTING NETWORK FAILURES NETWORK CONTROL AND MISSION CONTROL FUNCTIONS PERFORMED IN SEPARATE HARDWARE PLAYBACK OF.GC LOG OR DELIVERY OF GC LOG EXTRACTS JPLWHEN REQUESTED BY FLIGHT E?ROJECT ^ CENTRAL - CAPABILITY FOR NETWORK TEST AND TRAINING AND COMPUTERS ' PARTICIPATION IN MISSION SIMULATION DSN DATA BASE MAINTAINED FOR NETWORK OPERATIONS NON-OPERATION-PERFORMANCE ANALYSIS DRIVEN DATA SUPPORT OF REMOTE MISSION CONTROL CENTERS PROCESSING Fig. 1. General configuration of the Deep Space Network j I' v JPL DEEP SPACE NETWORK PROGRESS REPORT 4Z--25 17 r n aQ ^D O - 6 H 10 '17 12 `10 -B -6 - 74 2 0 2 -- ; - 90°' iZ0° 150° 180° 150° 120° 40° 60° M. 0° 00° 60° Fig: Z NASCOM network circuit routingxhertuyi ^u ee t 1 ; 6 ^ 3 COMM SATELLITE COMM SATELLITE i j NASCOM COMMON NASCOMGREENBELT NASCOM DSS 63CANBERRA CARRIER GSFC MADRID ROBEEDO J FAX 5 n DSS 43 STDN MIL ' . 8AI LIMA GAPE CANAVERAL 'I GCF 20 CENTRAL COMM JPL BLDG 230 I CTA 29 GCF IQ . DSS 14JPL BLDG 125 GOLDSTONE GOLDSTONE e i NASA I HEADQUARTERS X Fig. 3.- Wideband Data Subsystem block diagram : ... in DEEP SPACE. NETWORK PROGRESS REPORT 42-25 19 ryp^q°."""'P'fra`^n. .rmt?:rzv^°°'^^4i +'.r. ^. •r". T•^T ^.^. ^.^^...'r- .. _ ip?^'.":!°^'^-°;T7`..p^:`3!!^^i,^^i'^r^h's+,^ , r r... : _,v.: •x4: y ;°r°-4 ^xx^::^'. r^:--.<. ..-... . ^.y ..^ u^..,.< .« ..,..-.., e, .:r.., -^.»r.^-. ,...--,-,c:^.....^.<^..a...z.»r:uwema:nay+^+-.-e..a^«^e.^.e.^ea^.e.,-.raw.,n^...:.T........^..^.,--__.__.__—._ DSEF :. GCF AT STATION(DCf) TRANSMISSION GCF AT JPL (ACT, 1ST) (CCT) _ OCIS, — ETC DDA 2 MYG DSS 14 DDA• CODEDMULTIPLEX WB WB CODED 2CIA 21 {l) DATA DATA MULTIPLEX NOCC 28 .5 kbps (Z)SET SET E . SCA MONITOR (1) (2) 2 LATIC ETER g DDA . 1 WB WB 42/#3 DDA CODED MULTIPLEX DATA DATA DISPLAY 61 /63 2 41i SET 28.5,k6pi SET (1) (2y SCA MONITOR WB SWITCH DDA r CODED MONITOR 1 STDN NEIL MULTIPLEX MTC (1 } LEA we wa r. DATA DATA m: SET 28.5 SET (1) (1) nPROJECT Wg m. LOCATIONS DATA(BOEING, CAPE SET CANAVERALI .(r} O we DATA 230,kbps WB D5514 DATA MTC SET SET *NOT EQUIPPED AT CTA 21 (r} (1',) r DDA - DATA DECODER ASSEMBLY SCA - SIMULATION CONVERSION ASSEMBLY Fig. 4. GCF 1973-1974 wideband date capability Aw M. M m - 53 CONTROLlD ROOM D5S GCF COMM TERMINAL ROOM - _l; TRANSMl5SION Z: FOR LOCAL LOOP TESTING ONLY MONITOR/SEARCH ALARM 7d YADEBAND WBDA CHANNEL i (PRIME) r.- DC PATCH PANEL ] DIS Rx l *-- _ J MN ^A' yw[j INTERFACE mS CODED MULTIPLEXER' FROM JPLDATA f . SCA ••— ® (CMD} — \1 DATA SET AUX.SET WOOL (28:5 kbp) FOXL _ . J .. / 303 BDfi TO JPL NASCOM WB SWITCH ^VYB GKT^a TTt""' LOOP BACK OPTIONS DDA 1 L TP-1 Tx 1 AC -- REMOTE TEST 1 ] DC - REMOTE TEST 2 — t —---o FEC 600I TEST SET TCP 1L J ..: OSCILLOSCOPE'----W-0 FOR GCF TESTING ONLY WB EQUIP DSS 71 CTA 21 DATA SETS 1 1(303) NASCOM 1 0W8 SW CMDs 1 1 NOTES: m STDN MIL AND CTA 20 NOT CONFIGURED WITH CODED' MULTIPLEXER SWITCH AND BACKUP WIDEBAND CHANNEL, AND HAVE ONLY ONE ODA WB INTERFACE DIS AND DDA ' COMPU.TER RECEIVE INTERFACES AT DSSs USED IN TES1 SUPPORT AND DATA VALIDATI0.N ONLY CTA 2t NOT CONFIGURED WITH NASCOM WB SWITCH Fig. 5. SMN MIL and CTA 21 GCF (28.S kbps) Wideband Data Subsystem assembly con iguratkm ' ^ ,_DSS CONTROL yl-,- _ _ - -- ROOM : DSS GCF COMM TERMINAL ROOM TRANSMISSION--e FOR LOCAL LOOP TESTING ONLY MONITOR/SEARCH ALARM WBDA CHANNEL . 1(PRIME) LDIS+" .j 0-8— RX t r — — — ^1 LOCAL DATA SET y WIDEBAND DATA WB INTERFACE AC LOOP BACK ` — PATCH PANEL t (A'6) ' . I CODED MULTIPLEXER FROM JPL/GSFC L rSCA (CMI7) T_ INT ( TEST SETA363 !. AUXSET WBDL (28 .5 khps) fDSJ . 806 TO JPL/GSFC FOR GCF TESTING \\^ ONLY NASCOM OPTIONS r ^ . WiDEBAND MATRtX / CKT (OOP BACK r TCP 1 ^-- --- P-2 TX SWITCH AC - REMOTE TEST 1 MODE `bC - REMOTE TEST 200DEL _: J I WB CODED rECTROIVICMULTIPLEXER [COUNTER/SWITCH ^ CIL ` OSLOSCOPE -- -^---r t- - i DMA 1 f L - P-1 FEC 600 ) L TEST SET o rn ^ WBDA CHANNEL 2 (BACKUP) rn i N ! r --- — — RK —^ J DD'A 2 IL_ CODED MULTIPLEXER DATA FROM DSC 1 0 . r I' (CMD) 2 ^-- -W- I TEST DATASET SX1T WBDL (28.5 kbps) FDX7C DbA 3 Is P-1 3M 806 . ^..... -- TO DSC 10. L (BACKUP CHANNEL DSS lb ONLY) (. N TX^^ In P?.. 6. Deep Space Stations 14/43/63 SubsystemGCIF (28.5 kbps) Wideband Data assembly Configuration N !N Lit JPL lGCF SWCINI BLDG 230 JPL.KCCPNOC AREAS 4, DIGITAL INTERFACE DCF INTERFACE ---.Alw"onATA A^.SEhLBLX_ POINT 10 GSFc WOSA SWITCH DSS4Y63171-AO GCF A WIDEVANDDUATAWB%lFOX)e&5kW GVOwb Tt MONITORI$us.OSS4316W.1-AO ALARM DATA COOED su q 'Auumputp 21.5 WflLD.4SPXl IMS kW M50 . DATA. 69 5 -0714,01A SO FIfANCI SCO SET' 6 mccc —mcu 28.5 Sim I ltxl Co W6LD . 0SFX1i2&5k.t SIMLAtIONGW59M CODED OSS43VIASANFRANCMD SET. A MUITIP . qLEXER cDmpu7ERf2 )C (V28.5 Sim 2 DATA I I-- MTC-' 'RX) SET 5 1, LDA MTC-, tRx) -oF 28.5 2 =( g^TO CIA 21 4-0 r I AITC WSK. IFOX) (2&3 khol DATA m7c --o -mo .0 0 SET 3 COMPUTERS DED IMOM CTA 21 - M^I^TIP VXER p- TO ,DSC lOfDSS 14 A c- 9 wc-3 tTxl . RXI, -129.5 LOA IWBOL .1 4FOX) MW 024 DATA 2 mccFMODEM 71 IRXI. IIODLTIP EJSP JI 9 ITC-3 tAR 'A L12 3M 75. : FROM DSC 10105S 14 SET I .,Ps TO DSC 10FOSS 14 IMKUP) YIRS -2 fRMJ ^ 1 1360-751 35WROL Z (FOX) MW DWA WBMomm LDASET I I FOR CAPE BLDG AD 3 USE DATA SETS IB OR 9 ONLY) INCS BLDG 202 E4 INCS TXfRX i rI ^I I k-' SFOF ^r---COMM TERMINAL-. GSFC-+k ^+----^-----MA4RiD SWITCH. TEST CONTRQL BIT PPR F600 __. 303C GW58619 309C' 3030 GW58530, 303C F600• s XMT XMT RCV XMT RCV RCV CLOCK F604*. RCV BIT BLOCK s ERROR ERROR PPR TO 6050 FOR ..LOGGING F600 303C GW58619 3030 3030 GW58.530' 3030 F600 RCV RCV XMT RCV XMT XMT F F600 FREDRICKS 600 TEST SET FREDRICKS 600 TO INC DE WESTERN RE5 RVEI .PBEC RCVRCV . ELECTRONICS Np. 1225 ERROR COUNTER t BIT BLOCK MODULE. BLOCK SIZE SET TO 6a0 bits Bit BLDCK PPR PRINTER-PUNCH-RECORDER PBEC PROGRAMMABLE BLOCK ERROR COUNTER,-- PPR MFG BY INSTRUMENT DISPLAY, inc GW58530 ` ROUTED GSFC-WASH. D. C.-ETAM. W. PPR V Nr IA-SUETRAGOSPAIN- i Fig. 8. Wideband Data Subsystem W-kbps test configuration, June 1971 ` n 24 JPL DEEP SPACE NETWORK PROGRESS REPORT`4223 . ' } w OSS CONTROLROOM ^- DSS EONTROL ROOM DS514 COMM TERMINAL ROOM MJWSMISSION ---^ Jj +--TRANSMISSIONw DSC 10 GCF COMM TERMINAL TRANSMISSION ---f1 .^ ! WU SUPER GROUP fGCF AREA ^^ 123D kbps) WIDEBAND r_^ 1230.4kEps1 TEST SET r^ i DCLOOPBACK ! LEASED T^OTJPL WESTERN UNION -- - ^ MICROWAVE 1 ACl0OP8AGK I BERT I O L. 240 kHz MW CHANNEL /^^ ANALOG EE WIDEBANDTO DSS 14 1 --_J PATCH I I DC PATCH / i I j PANEL I_ I PANEL j f-(TEST DATA ONLY TO DSS 14 - \ (A-4} DATA SET! I_ (A-4) /' I WU WU FROM JPL_I__ W$OL(230 :4 k6ps) MODEM ' / DATASET DATA MODEM i WOOL [FDX) 230.4 kbps f -. .CHAN 1 TOM 522. . TOM 501 TDM 520 FROM DSS 14 IGCF) ^. _ ^. ILEASED) (LEASED} TO JPL i SIC1117.6 kbps1TLM DATA 1 1 —Ir BACKUP ^^^ GCF AREA MW rSN WiCROWAVEI: EU2) RADfO^CIJ I. CHANNEL I MONITORING I DCLOOPBACK } I ) `TO p55 14, ...L CGi1FIG =^ ^ I I ,^-. T-•F j ♦--^ _ .. _ \^l_ r DATA SET! ' o.- •- r-^ WU ^ ^-=^ f .4 kbps) _CHAN 2 - I MODEM I TOM 522 DATA DATA wIJ e , MODEMl D1 -J TOM 520 GCF QD5ET iPARE) (SPARE) L `,^ ^.^ L _—^ I (SPARE) -- € SEPT 73 Q GCF BACKUP 230 kbps WB (CHAN 2) DSC Q WU BACKUP DATA SEr1DATA MODEM PATCHING T Z TO BE ACCOMPLISHED BY WU PERSONNEL ONLY10-TO-DSS 14 WILL NORMALLY 8f SCHEDULED BY J. GCF AND REMAIN IN HOT BACKUP CONTINUOUS Q FOR BACK CHAN DETAILED Z kbDs-WB TERMINALTEST MOOE DURING EACH DSS 14 PASS SCHEDULED FOR REALTIME TX OF 117.6 E4UI Whit CONFIGURATION REFER TO GCF SOP E: . 844^182`^0-A1U9.SIC TLM DATA. Fig. 30. DSS 10 communications terminal GCF (230 kbps) Wideband Data Subsystem assembly configuration t 3 3 26 JPL DEEP SPACE NETWORK PROGRESS REPORT 4215 ir i 1 t .IPL-GCF SWCEN (2?0 kbps) JPL-GCF SWCEN MCCC OPS AREAS WIDEBAND ASSEMBLY MVM 73 CONFIGURATION MTCF (MTC) BLDG 230 1 11NOTES MTC COMPUTERS m GCF SWCEN BACKUP DATA SET/DATA MODEM PATCHING WILL BE PERFORMED AT ANALOG SIDE OF WU MW MUX EQUIPMENT BY WU PERSONNEL .ONLY 1218/1530 a FOR ADDITIONAL DETAILS ON GCF SWCEN WORD WORD(230 k6^ ) WB TERMINAL EQUIPMENT CONFIG REFER TO GCF SOP 844-182-10.4109 ® MTCF CAN LOOP BACK. GCF SWCEN DATA AND I FORMATTER 1 FORMATTER 2 T TCLOCK SIGNALS AT GCF MTCF COMM . INTERFACE PATCH PANEL ... ® FOR GCF SWCEN-MTCF TROUBLE ISOLATION- CF GOMM INTERFACE PATCH PANE PROCEDURES SEE GCF SOP 844 =170-2U-4501 MTCF-GC F 1 I - INTERFACE 1 SD SGT SCR RD" SD SCI SCR RD TRANSMISSION -F E .. --- _.. — I _.. . JPL-GCF SWCEN (BLDG 230) +4_ , ) ! Y CABLECABLE MTC, - I ^L^ 117-2DATA SET . ^ AG LOOP BACK L— 117-1 ,^ TOt MTC^. l— \ SD SGT' SCR RD , .. SD SCT 5CR RO i WESTERN UNION LEASED 240-c1iz —_ \(230 kbpt) (230 kkips} PATCHANEL (A-XX). t SUPER-GROUP CHANNEL DC. m PATCH PANEL A0 ( RD` L r .. 5Q SO, RD a I If FDX^ DATA `N.. (DA'b p^ _, (230 kbps) ( MODEME D^ffA TEST SW} I LDA.2 .. ., GE 52l) v WBSA RACK ...=SPARE.— — -1 242/WBD3 - WU DAtA TA SETMODEM G E 520 G E S+J1 ( :. _ (230 kbpir) 1 BERT 901 - E TEST SETE, Fig. ii: lPC.(GCF SWCEN) (230 kbps) Wideband .bata Subsystem assembly configuration " JPL DEEP SPACE NETWORK PROGRESS REPORT 42-26 - 27k H7 HSDL WBD# RECEIVE EQUIPMENT y^ TO DSS MCCC .HS DE WBgL_ GCF TRANSMIT EQUIPMENT qtILOCK 1BASEMENT BUILDING 230 NDP COMM PDP-6 ;. PROCESSOR B/U I(PDP-8) I L DSN OPERATIONS c, CONTROL AREA BUILDING 202 ffNDPR EAL NDP DISPEA E AND CONTRO MAG TAPE'I . , .. NDP OFFLINE MAG _ 3 TAPE _ - PROCESSOR z I (£5) ' FIRST FLOOR BUILDING 230 r Fig. 12. Block I NDP configuration i I - a 2$ JPL DEED , SPACE NETWORK PROGRESS REPORT 42.25 a r.- 3 I .. LDM33 .I - - - - - - - BMXR PATCH- - - - - - - AND TEST - - - - PANEL I +- CPS ... A Sim .. i NOT i 2 MTC ENCODER 1 .} _ HSD DA7A SET - _ WAXR I - - DECODER - .... _.. CPS MTC I I I ^ • - - 5AME AS BMXR I - l 200 ENCODER HSD VTA SET BMK¢ 2 1 L . I-. - _ - SAME AS _ ... .. RFAXR 1 1D3 _ ... ENCODER - .. I- - _ - _L -HSD DATA 3Ei ECODER -^ .. - I .. - SAME AS BMXR I - - - HSD. _ 2W- ENCODER DATA SET - W - {^LCOV-- - I I h . SAME AS BMXR l 1 ENCODER _ DATA SET DECODER .2^. ^ -BMX3<-S - Cr -- _ TYPICAL - .,. REMOTE MOC- PATCH AND I4g4gEQUIPMENT'CONFIGURATION - SAME AS BMXR I - CNCODER HSD[RMCX1 . BMXR 6DATA SET I SAMEAS SMXEI I HSD20.3 ENCODER - ^ - DECODER^ - -DATA SET 6MXR 7 I^ I T ;' a 1 3'. SAME AS'EMXR 3 I I I I - - k5Q DATA SET. - RMXR 8-12 ).. I _ f.cioECOOF.^ J swnCHwG ^ i — — — _ ..-.. ....^ — .,. ^.... . ^ _ — _ _ _ — 1 RMOi I %I FILLER PMOC . MU% NCS I IYOLTAGL:{i •. w.... ..... _. ....r _ .•..^... _ L CURAINck IINOI USED) apl - ... W6 - ENCODER - - - - wiso D A SET BDXR _ we DECOOEa JPL DEEP SPIKE NETWORK PROGRESS REPORT 42-25 POLDM or POOR QUALM x GCF INISFACE AREA BLDG 230 BASDMT PDP&L I coN A PANEL PDPg,L .:. _ IM) - - — - ^ [EaCKL1P1 - 11_ i IIY PAPE0. TAPE _ _ AEAPERRUtaCH ^ - - - - ^^ E TX I I ? I -1 ! 1 i 1 I -' - - Tx old 1 1 - - 1 - -—:. AX I } I 7x t f OL RI[ 1 I - 7Xt I Im I I I —7 .. - ^1 I: 1 %. VOLTAGE'CUPPENT bD%R 2 - - 1 RX CONVERIEA - DATAt S17- r^^---7 1 1 L —. --J PATCH .. To NB.. 1 F^.. PANEL `! C S - 6CDG T42. -- — — — — — — — - I WED ; _. t SDI ILI" r..—^ _ 7x 1 1 L .. .. 1 I R% 1 I L - - - - -^. . -_ _ I IPAOGaAAnMNIKOLLf" 1 fro ... r '. SMlICNSNG .- ^ I''CRNTRQLLEA..1. .! ... 78ANSAl1TlRECE [ VE BUFFER ASSY. I Hari,- i CWINNELS f•tr A7E MOD-&OWaAL IHIOUGH-... - - - - CHANNEL,$ 1-12 MAY AE SL%117tGTt p FOR ANY 6VAGE/ NORIAAL.7H8OUGH-: CHANNPL .. AAENi.:: Fig. 13. Block I NI)PT configuration s i - 29: C: _ I — ^ ExTERNAL NASA 35.617 TIME CODE TIME CODE IN7PFRCI 1RANSWOR 15 CPU 1 PPS SYNCH_ ( (8231] MEMORY AK WM9RY Jr. - - - - - 16231] IE^EI - OSCILLOSCOPE ( CLOCK k[AI TIME I.I MEMORY INCR MDM(3KY IN[R . 4K (8252) ;K rS 52J .R #A) (921 1) + FLOATING .; - NASA 36-611 I OINTPOINT AP1T1i [921} MLMOKY I74CR MEMORY iNCR 1 PA'ALLEL 6C0 sK f92571 /K IEI52VI ^ - SIORED INPUT INTERRUPT - I : PARALLEL NNARY.. SB E0.) (7P55) (9121) MEMORY. INCR MEfhDPY IFJCR )MODULE CONTROL AK 48252T 5Y57#M ,PPS INEERAUP7 INVERSION AND - ( INTERFACE 1 KPP4 PRIORITY5_. I PP SWITCHING ASSEMBLY - UNIT (7934 (A EA) (BZ22) I'. INIEARU4 - ADDITIONAL CONDITIONER - {16) REG BLOCKs. I .. .. I.KPPS (7942) LEZ161.i2 [0.1 . POWER MEMORY PORT EXPANSION [MEMgRY'SLLEC.' FAIL-SAFE 'I _ (8213) MEMORY 7PROTECT GMT DISPLAY GMT DISPLAYI NEkA70CODE , TIME CODE I INTEGRAL CARD READER/ PAPER TAPE Y,EO'33 I f GENER0.iOR' ^ GENEVgTOk2 l,.' I I $10 CONTROLLER PVNCIIREADER! CONIPOLLEt { 1 PRC/CES500. _ {7127], CONTA I7fl5fl1 {712! y77. - I PREOUENCY' - TOP 6U5 I' STANDARD ' { .. .. TENSING ASSEMBLY t10 vVPt) J AREA I R] - - QO GCF 410 DISPLAY - - - CONTROLLER - INTERFA CE AREA RFBAOIE CONTROLLER - CONTROLLED, 41071CC-16 WIDE -BAND 6A3CH- - -7641,02. - 76 :i - ART, - LINE)) TEUAINAL) r, 11 401 DATA S£1 TOIFRC M CCF 20 I 1[. r... ..... . E{ [. I _ .: (TO GCF ^•14915PLAY CONTROLLER 3. ... .. BLDG 230 iBA5£M£NF] COfJEROLif .LT4?. F : TT CONTROLLER INTERFACE AREA REMOTE ... A RT.)CC-35 WIDE MAN% BATCH 7601/42 7601 AIE _ _ I UNE) TERMINAL), r. DATA SET 401 _ (10 DBPLAY^I - I(IP BUS AREA YSR) L- INTEGRAL 110 CARD AFADEA/ PAPEq TAPE K R-3Y - - PROCESSOR - - CON7ROtlER PUNCH/READFA.' CO^'ITWSF - - - _ (7126} CONFR £7La01 %xp . - MEMORY - PROTECT I92T41. POWER - - - FA11- SATE a - - PARALLELMEMORYPORTEx.?AN510nfNTMORY 1.1^ ,. PARPLLEL SPORED INPUT ADVItIONA, 5 . .... rAODULE 1161 REG BLOCK .. - I .BINARY . (g EA)CM51. .. (971610 EA ) , - SYs1EM TPPS INTERRUPT I - INTERFACE PRIORITY UNIT (7439! (4 EAT (EMT PPS MEMORY INCR Mt/M-^RY IIw.'.P d - - - INTEPRUPT INTERRUPT- 4r 0257) sr, fE:57PCONDITIONER CONTROL ) 1 KPPS - . MEMORY IuCk WMIJZ+ i Ntl POINT INT ARAIH AK [975 A K Or7 5 ' N:MOPY]NC ~0TY#NCPR#Al TIME At. (9758) sR: IFI571 CLOCK II !ATMORY fY... ME!r ^Y ir' - L5 CPU (925q (67511 1 E%TEAM►L INIEAFACi Fig. 34. Block. t NDPA. block diagram 30 'N ouT r^ I +^. Iy 1 i ! i NETWO1 PROCESSING. BLBS MEMORY AK0 AK I} (B251y INCR MEMORY INCA 521 AK 102571 'INCR MTMOAY INCR 52) AK 10757] ?INCR MEMORY INGA . Sty AK 10152) SI GMA-5 A STR ING WAORYSETION) 1825Ay.LEC TAPE UNIT TAPE UNIT TAPE UNIT TAPE UNIT LINE PRINTER-Irunl CRT Illy ISIY KBJCONTP. OUEA(ac ID* HAR6COIY. {J01;)(73211 (7522) (7322) (7367) ^' RAPIDACCESS DISK. - .. STORA I GE [72OR1 / N.LER MIILT$PLEX IlO P1gCE550A MAG TAPE CONEROLLER (4 TRACKT (77295 MAO TAPE CONTROLLER. I7 TPACK} RAPID ACCESS DISKCONTROLLER {J2DE) PRINTER CONiRQLLEA CONTACKLEA {LOCAL 3,'2 DUPLEX) (CC33I7) _I _ - (6273) - - .. (73;1-7355 _..:... ) - ..... (72 0) = -- - - 3 . DISPLAYjT0 ..... ... 30P 6U5 .. .. .. ... . I ' DATA 503 t7 AREA KSRI .I7 ^I:LER (TO DISPLAY] AREA ISSL . - - - - - _ (TO DISPLAY AREACONTROLLER -CRT; HC/K8) - B CC73C PATCHING ASSEMBLY (INPUIS TO ON-LINE AND BACKUP SYSTEM) - - - - 2 KILOM} DRIVER ,^ - PATCHING ASSEMBLY TUITS OF ON-LINE AND BACKUP SYSTEMSMI - - - ..::OLLERDO DISPLAY .. CONTAOILEA [TO DISPLAY AREACRT/HC/Kg) IAREA KSR) CC33C _ 2 A KILOq AR EA ISPLAY IOP BUS 111 DRIVER l .. ....... ! IrF+r a4rvEi a571 35f pLLER MULTIPM WO PAOCESSQR - MAG TAPE CONTROLLER - [9 TRACK) 17320) MAG TAPE. CONTROLLER(7TRACKS RAPl9 ACCE`-S DISK PRINIE0. CONTROLLFJi - CONTAOLLER (LOCAL Ii'2 DUPLEX) {CC33DS I 5 q {6773) - - - - (7740.7JL5k . CONTROLLER (72011 (17A01 -;§ RAPmaccess olsK SPORAGEI72 .;i0-.k , c l to MCTs or ON-1's arc not included in these estiniates. Categories of readi.tess: A Support planetary \ L- mic'atlon tvs(ti f tL•lenietl}' and command) B Support planetary veriftcation tv5ts (tTacking find wonitoring) C Support launch phase s5'slt'irt inlegration tests D Block IV receiver eonunitted A DSSs 4:3 and 62 F Support phlnclary phase system ir-.c :-Nation tests MILESTONES J F FM DSS 11 HARDWARE /!SOFTWARE IMPLEMENTATION NOTE SYSTEM PERFORMANCE TESTS OPERATIONAL VERIF TESTS j PERFORMANCE DEMO TEST DSN/VMCC INTEG TESTS SUPPORT FOS TEST AND TRNG DSS 14 HARDWARE/SO ARE IMPLEMENTATION NOTE: SYSTEM PERFORMANCE TESTS OPERATIONAL VERIF TESTS PEPFORMANCF DEMO TEST t j DSN/VMCC IWTEG TESTS i ! SUPPORT FLIG 4T OPERATIONS SYSTEM TEST AND TRNG i Fig. 2. Extract from DSS JPL DEEP SPACE NETWORK PROGRESS REPORT 4 1974 1975 1976 MILESTONES J F M A M J J AS OND JF MA M! J A S O N D J F M A M J J A S O N D NASA SUPPORT PLAN PRELIM FINAL LAUNCH I L PLANET OPS DSN PROGRESS/READINESS REVIEWS PLANET VERIF ^ 1w I D5N/VMCCC INTEGRATION TESTS GTA. 21. DSN/VMCCC INTEGRATION TESTS MIL 71 DSS ll, 14 DSN/VMCCC INTEGRATION TESTS ^ ! I I l DSS 42/61, 43/65 DSN/VMCCC INTEGRATION TESTS L&CDSS 12, 44, 62 ! ; DSN'VMCCC INTEGRATION TESTS/ I CTA 21 AVAIL. FOR I SUPPORT (FCT) It 71 , ALL DSS PLANET \10, VL, FOS TO DSN COMPAT.TESTS VO, VL, FOS TO DSN COMPAT.TESTS DSN AVAIL. TO SUPP VIK TESTS DSS 11 AND 14, L&C AND TNG I ORT-B :+7 AI TO SUPP VIK TESTS i RT-A PLANET. AND L&CDSN OP READINESS FOR SUBNETS PLANET j DSN OP READINESS FOR SUBNETS INEP OP READINESS REVIEW UPDATE I I FINAL i _4#_[ 1 .1 NEP OPS PLAN VOL. IV SUPPORT PROJECT READINESS REV IEWS I I ! 1 1 11 71 LAUNCH PRE-ENCOUNTER NOCC LAUNCH AND CRUISE SUPPORT I BLK Ill NOCC PLANETARY SUPPORT INCL IDR - — INTERFACES , TRAJ DES DATA FROM RSSP UPDATE FINAL S/C AND LV ANTENNA PATTERNS tT TD O SPDATE SPACECRAFT SIRD AVAILABILITY OTDA REL TO JPL f RSSP - RANGE SAFETY SU°PORT PACKAGE Fig. 1. Extract from TDS schedule, Level 3 for November 1974 1974 1975 1975MILESTONES J F M A M J JASON D J F M A M J J A S O N D J F M A M J J A S Q N D RECEIVER/EXCITER SUBSYSTEM RECEIVER/EXCITER BLOCK 1V 5UBCARRIER DEMOD ASSEMBLY j I 4 X-BAND OPEN-LOOP RECEIVER MODS I ' I RANGING DEMOD ASSEMBLY DSN SYSTEM PERFORMANCE TESTS j I TELEMETRY i C P COMMAND I C, P p TRAGIC ING C, P1 j I P TEST AND TRA I NING C, MONITOR OPS CONTROL C, p MISSION PREPARATION TESTING I I ^ I I. 1 DSN/VMCCC SYSTEM INTEG C, P I p OPERATIONAL VERIFICATION I Cr P I P PERFORMANCE DEMONSTRATION C P I CONFIGURATION VERIFICATION I C _ I € I C = CHUISt P ^ PLANETARY Fig. 3. Extract for DSS 14 milestone schedule for November 1974 DIVISION 3:3 COMPILES ENGINEERING DATA BANK ORGAN IZATION 424 COMPILES OPERATIONAL DATA BANK DSS DIRECTOR ESTIMATES "SUBSYSTEM COMPLETE" DA-T,S I ESTIMATES "MGT/ OVT ` COMPLETE" DATES VIKING PROJECT OFFICE DSN MANAGER TDA OFFICE YES PROVIDE PROJECT ASSESSES "CAN DSN ACTIVATE NEED DATES MEET COMMITMENTS" PLAN NO YES _ TDS MANAGER NO RENEGOTIATE PROJECT NEED DATES Fig. 4. DSN/Viking readiness plan 42 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 Helios Mission Support P. S. Goodwin DSN Systems Engineering Office The fist of two Helios spacecraft, built by West Germany, was successfully launched from Cape Kennedy on December 10, 1974 and is now enroute to an unprecedented 0.31-astronomical unit (AU) perihelion in mid-March 1975. This article describes the DSN support starting with the prelaunch activities and carrying through the first three critical days of the mission. 1 I. Introduction The previous article (Ref. 1) discussed the results of the Helios prototype model spacecraft compatibility testing that was conducted at Cape Canaveral, Florida, utilizing the Spaceflight Tracking and Data Network (STDN) (MIIx71) facility. This article covers the compatibility testing of the flight spacecraft (F-1) and its subsequent launch on December 10, 1974 from Cape Canaveral, the initial DSN acquisition of the flight spacecraft over Australia, and the DSN support during the Step I and H maneuvers that occurred during the first three days of the mission. II. Prelaunch Activities A. Flight Model (F-1) Compatibility Testing The Helios-A flight model spacecraft (F-1) arrived at Cape Canaveral on September 22, 1974 and was transported to Hangar AO, where it was assembled for testing of its compatibility with the DSN. Compatibility tests using the STDN (MIL,71) facility commenced on October 25, 1974 and continued for 68 hours. With only one minor exception, these tests showed that the F-1 model spacecraft either duplicated or exceeded the performance characteristics demonstrated by the proto- type model spacecraft during the latter's compatibility tests in July/August 1974 (Ref. 1). The minor exception was that the F-1 spacecraft transponder has a range code polarity inverted from that measured with the prototype model spacecraft—however, this difference is not signifi- cant since the DSN Tracking System is capable of supporting either it normal or an inverted range code. The Helios flight model compatibility tests also demonstrated that the DSN's corrective steps to overcome the difficulties detected during the prototype compatibility tests at Cape Canaveral were successful. The overall success of the Helios flight model spacecraft/DSN compatibility test effort gave reassurance that Helios-A could achieve its December launch opportunity. B. Initial Acquisition Backup by DSS 44 With Pioneer 1.1 Jupiter encoanter operations occ-rring very close to the contemplated December 8, 1974 launch of Helios-A, the DSN became concerned about providing; redundancy within Australia to perform the initial acquisition of the Helios spacecraft. Prior planning; had assumed that the Australian 64-meter station (DSS 43) could be employed in case of an emergency to provide backup support to DSS 42 during the initial acquisition. However, Pioneer Jupiter encounter requirements dic- tated that DSS 43 be exclusively devoted to the Pioneer Project—hence, there would be no backup to DSS 42. While no backup Ausiralian station had been committed to the Helios Project, the DSN realized the importance of an early initial acquisition in order to perform the Step I maneuver and, therefore, took steps to see whether or not the scheduled conversion of the STDN Honeysuckle Creek facility to a DSN station (DSS 44) could be accelerated sufficiently to provide an "engineering level" support during; the first pass over Australia. A tc:etype message presenting this proposal was sent to the Honeysuckle Creek facilit y on November 4, 1974. The station responded that they would give it their best effort and appreciated the DSN's offer of assistance. While a considerable amount of the necessary equipment was already located on site at Honeysuckle Creek, much remained to be done to implement the hardware and to debug the special computer software programs which were dictated by the Honeysuckle X-Y antenna mount. In addition, it was desirable to arrange for the loan of an STDN acquisition aid antenna front Goddard Space Flight Center and to remount this antenna on the quadripod of the X-Y antenna. Completion of the implementation, plus at least a minimum amount of operator training, was desired prior to the Helios Operational Readiness Test (ORT) scheduled for Decem- ber 5, 1974. All of this was very successfully accom- plished—which is certainly a tribute to the personnel at DSS 44. While many of these station personnel had prior tracking experience during the Apollo Program, few, if any, had prior experience with the DSN or its procedures. Therefore, their efforts are doubly appreciated. C. Helios Operational Readiness Test The Helios-A Operational Readiness Test (ORT) was conducted on December 5, 1974 with the DSN configured as it would be on launch day—including all backup DSSs. This was the first (and only) exercise of the newly implemented DSS 44 in a Helios Project test. (Prior training had been on a DSN internal basis.) During the ORT, simulated failures at DSS 42 (Tidbinbilla, the Australian prime station) were exercised with DSS 44 assuming responsibility for the "failed" function at DSS 42. This included a simulated 100% failure at DSS 42. DSS 44 performed well under all simulated conditions. The ORT also simulated the Step I maneuver and science turn- on sequence over Australia, the near-Earth science return over Madrid, and a Step Il maneuver sequence over Goldstone using DSS 12 as the prime facility and DSS 1 I in a hot backup capacity. All DSN facilities performed well during the ofa. This fact, plus a favorable Mission Readiness Review held at Cape Canaveral on December 6, culminated in the Project Managers' decision to attempt a launch of flelios-:t on December 8, 1974. 111. Launch Activity A. December S, 1974 Countdown Preparations were commenced to launch Helios-A on December 6, 1974 with the opening of a 42-minute daily launch window at 017:16 GMT. During; ti ►e minus count, all supporting DSN facilities began their pre-track calibration sequences. Besides STDN (MIL-71), DSSs 42 and 44 in Australia, DSS 62 in Madrid, and DSSs 11 and 12 at Goldstone were involved in this first-pass countdown procedure. At T - 10 minutes in the countdown sequence, which was at the point of a built-in hold, a launch vehicle telemetry readout from the Centaur liquid hydrogen engine caused some concern. The T - 10-minute hold extended into the opening of the launch window, but the Centaur telemetry problem was not resolved. The hold continued until approximately 20 minutes prior to the 07:56 GMT close of the daily window on December 8, at which time it was derided by the Project Managers to "scrub" the launr_h attempt for that day. Shortly thereafter, the Project Managers made a decision to reschedule the next launch attempt for December 10, 1974 in order to avoid unfavorable weather forecast for December 9, as well as to provide time to thoroughly diagnose the problem within the Centaur stage of the launch vehicle. B. December 10, 1974 Launch of Helios-A The launch countdown of Helios-A resumed on Decem- ber 10, 1974 towards a targeted opening of the 42-minute daily window at 07:11 GMT. Again, the DSN stations at all three longitudes participated in the minis count by performing their pre-pass calibrations and dataflow tests. This time the launch vehicle proceeded through the T - 10-minute built-in hold and continued satisfactorily right up to the opening of daily launch window. Helios-A lifted off the pad at Cape Canaveral at 07:11:01.5 (hours:mi- nutes:seconds) GMT with all subsequent launch vehicle events occurring on schedule. Early radar tracking from the Eastern Test Range Radar Stations indicated that the trajectory was entirely nominal. This fact, plus confirma- tion from the down-range telemetry stations that the 44 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 Helios spacecraft transmitter signal was "on the air" gave confidence that a nominal initial acquisition procedure could be employed by tine Australian OSSs upon spacecraft rise. C. DSN Initial Acquisition Following a perfect lautieb trajectory, Helios-A space- craft was acquired by the Australian DSSs at 07:57:33 GMT with DSS 42 providing tite prime source of data and DSS 44 acting as a hot, redundant backup. During this time, the spacecraft's attitude was such that its signal as received by the Australian DSSs was being transmitted by the dipole (top) element of the omni-directional antenna (see Fig. 2, Ref. 2). However, as the spacecraft gained altitude during its trajectory over Australia, the aspect angle changed such that the DSS reception would be via the (bottom) circularly polarized horn element of the omni-directional antenna system. The spacecraft radiation pattern boundary between the top dipole antenna and the bottom circular horn antenna element of the omni-antenna system created an interference region. This was of concern to both the Project and the DSN with respect to whether successful telemetry reception could be achieved during the transition. However, during flight, the signal degradation caused by this interference region proved to be less than had been feared. Once the spacecraft's trajectory had carried the aspect angle past the interfer- ence region, commands were sent by DSS 42 to initiate the Step I maneuver sequence. IV. Early Mission Support A. Step 1 Maneuver The Step I maneuver orients the spacecraft such that its solar panels are uniformly illuminated by the Sun, but with the spacecraft's spin axis still lying essentially in the plane of the ecliptic, i.e., the plane of its injection. This maneuver is required for both electrical power and thermal control. At the completion of the Step I maneuver, the spacecraft was still rotating at its 92.8-rev/min velocity imparted during its spin-up prior to injection. The next sequence was to deploy the magnetometer booms (Fig. 2, Ref. 2)—a process that caused the spacecraft's rotational rate to decrease to less than 55 rev/min. Following the magnetometer boom deployment, the radiowave experi- ment antenna booms (located at 96 degrees to the magnetometer booms) were also commanded deployed. Early telemetry analysis indicated that one of the antenna booms did not deploy fully; however, the Helios Project decided to defer investigation of this possibility until the spacecraft had achieved its cruise phase confilniration. With boom and antenna deployment completed, and the spacecraft still lying in the plane of the ecliptic, the next mission sequence over Australia was to initiate selected on-board science experiments in order to measure the solar wind how wave that surrounds Earth. This was also successfully accomplished over AlLindia, B. Near-Earth Science Return Following science instrument activation, DSS 42/44 in Australia and DSS 62 in Madrid, Spain, processed the cislunar science telemetry desired by the Project. DSS 62 performed very well during this first pass over Madrid, during which the Helios Project began p.•,,parations for the Step II maneuver following the subsequent Goldstone rise. C. Step 11 Maneuver Sequences Following Helios-A spacecraft first rise at Goldstone, the spacecraft telemetry format was changed from science to engineering data in preparation for the Step 1I maneuver. At this time, the spacecraft was well p::st lunar distance so the near-Earth science had been accomplished. The first series of Step 11 maneuver commands caused the spacecraft to yaw within the plane of the ecliptic to c• 4ibrate the thrust of the cold gas attitude control nozzles. After this was accomplished, commands were sent to pitch the spacecraft such that the antenna mast began to move towards the North Pole of the ecliptic. During the early portion of the Step 1.1 maneuver pitch commands, the spacecraft attitude was such that DSS reception was via the off-axis horn antenna out of the bottom of the spacecraft. As the pitch angle increased, so did the spin modulation on the dop.pler frequency increase—thereby giving an indication of spacecraft attitude in the tracking data. The spin modulation doppler signal was usable up to the point where the interference region was being traversed. To traverse the interference region (a feat requiring numerous commands), the Helios Project, in cooperation with the DSN, requested horizon- tal (ecliptic-plane) polarization at DSS 12 and vertical (perpendicular) polarization at DSS 11, with both stations supplying spacecraft telemetry via high-speed data lines to the Mission Control and Computing Center in Pasadena. This technique enabled DSS 12 to communicate with the spacecraft via the horn antenna while DSS 11 was communicating via the spacecraft's omni-dipole antenna. The point of equal signal strength reception between DSS lI and DSS 12 represented emergence from the interfer- ence region. Since the degradation of the signal was not as severe as had been feared, the interference region was traversed with a telemetry margin of + 10 dB at a 128- JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 45 bit/s engineering data rate. Following emergence from the interference region, DSS 12 was switched to vertical polarization, and the spacecraft downlink was switched from the ornni-antenna system to the medium-gain antenna system so the Goldstone DSS's received signal strength (AGC) readings would indicate the commanded traverse of the side lobe pattern of the spacecraft's medium-gain anterma (Fig. 2, Ref. 2) and also indicate when (lie peak of the main lobe of this antenna had been located. By the end of the first Goldstone pass, the spacecraft attitude was such that the mediurn-gain antenna pattern was very close to its peak value— indicating a nearly 90-degree orientation of the spacecraft with respect to the plane of the ecliptic. By this time the Helios Project's prime Mission Operations Support Team had been up nearly 24 hours (since many had participated in the prelaunch activities), so the reactivation of the on- board science instruments was deferred to the second Goldstone pass. Further Step U maneuver orientations were consequently deferred to the third Goldstone pass, during which time the exact center of the main lobe of the spacecraft medium-gain antenna was accurately measured and the spacecraft's attitude accordingly determined. Prior to this, during second-pass activity, the spacecraft spin rate was increased to nearly 60 rev/min- though not exactly 60 rev/min per the experimenters' real-time request. With both the spacecraft's spin rate and attitude in the cruise mode, the last engineering sL luence of this series was to position the spacecraft's high-gain antenna (Fig. 2, Ref. 2) such that it was directed towards Earth. This was accomplished by commanding various phase adjustments to the despin velocity until the mail: lobe of the high-gain antenna had been determined through DSS receiver signal strength measurements. This completed the intense past-launch Helios activity, and the mission settled down to its primary objective of achieving science return enroute to its perihelion passage of tlae Sun. V. COnclusions With the successful launch and orientation of the spacecraft, I•lelios-A has now been officially renamed Helios-.1. This feat was the culmination of approximately .10 years of effort on the part of both NASA and the Federal Republic of (West) Germany. The DSN is pleased to Ile a part of this effort. Helios-1 is now on a trajectory that will carry it to a 0.31 .astronomical unit (AU) perihelion in mid-March 1975. Its orbital period is 190 days, and its inclination to the plane of the ecliptic is 0.016 degrees. Since Helios does not have course correction capability, achievement of the above targeted orbital parameters was accomplished by the Titan-Centaur-TE-364-4 launch vehicle using the Centaur guidance system. Future DSN support of Helios-1. will continue to provide continuous coverage throughout the primary mission, with special emphasis on the first perihelion passage and subsequent solar occultation. Following that, the DSN will provide scheduled support through the lifetime of Helios-1. In addition, both Project and DSN activities are now starting preparations to launch Helios-B in approximately one year. References 1. Goodwin, P. S., "Helios Mission Support," in The Deep Space Network Progress Report 42-23, pp. 19-21, Jet Propulsion Laboratory, Pasadena, Calif., Oct. 15, 1974. 2. Goodwin, P. S., "Helios Mission Support," in The Deep Space Network Progress Report, Technical Report 32-1326, Vol. II, p. 22, Jet Propulsion Laboratory, Pasadena, Calif., Apr. 15, 1.971. 46 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 F ' I IS i ir. I I. s i DSN=MVM'73 S/X Dual-Frequency Doppler Demonstration During Superior Conjunction K. W. Yip, F. B. Winn, and S. J. Reinhold Tracking and Orbit Determination Section During the Mariner Venus/Mercury 1973 (AfVM'73) mission, the SIX dual- frequency doppler calibrations (for plasma and ionospheric charged-particle dynamics) have been demonstrated to improve post-/light radio metric doppler reductions: the error of one Mercury I encounter position estimate was reduced by 500 km (- 80%). This demonstration used tracking data acquired from March 16x29, 1974, The Sun-Earth-probe angle (SEP) was greater than 30 deg during this time. As the SEP decreases, SIX calibrations indicate dramatic increases in plasma dynamics. Simultaneously, the noises of the S and X dopplers and the SIX calibrations increase by 2 orders of magnitude as the SEP decreases from 30 to 3 deg, When these calibrations are used to support Mariner 10 navigation, unreasonable results are obtained. The calibrations, their noise characteristics, and their impact on Mariner 10 navigation are herein outlined. One possible cause for this behavior is that multi-pathing of radio signals to Mariner 10 produces phase scintillations of the S-band uplink transmission in excess of a/2 rad/s (3,5 cm of integrated phase change per second). This probably exceeds the linear performance region of the second-order phase-locked loops. I. Introduction of the demonstration around the superior conjunction period from May 27 through June 9, 1974. The successful demonstration of the SIX dual doppler experiment for the pre-Mercury I phase of MVM'73 has A study of the superior conjunction SIX dispersive been reported in Ref. 1. This article reports on the status doppler reveals that those data are excessively noisy JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 47 (approximately 0.5 Hz). Moreover, when the derived charged-particle information was applied in the orbit determination (OD) process, the resultant statistics were seriously degraded and the second Mercury B plane solution was moved by an unreasonably large amount from the uncalibrated solution, which was in fair agreement with the best pre-trajectory correction maneuver 5 (TCM5-July 2) estimates. In the following paragraphs, the characteristics of the S/X calibrations will be investigated and the data noise will be discussed. The orbit determination results for this data arc will be briefly presented, and, finally, a report will be made on the status of the investigation into the origin of the noise. II. Noise Characteristics of the S/X Dispersive Doppler Calibrations To put the entire SIX dual doppler demonstration (up through June 9) in perspective, let us begin with a study of the noise characteristics of the pre-Mercury I S/X charged-particle calibrations. Figure I shows the noise characteristics for the March 24, 1974 pass. This is one of the passes from the successful pre-Mercury I charged- particle demonstration. Application of S/X calibrations to this 9-day are improved the quality of the doppler fit by reducing the sum of the squares of the doppler residuals by over 70%. Also, errors were diminished by 80% for one Mercury I encounter plane position estimate, based on a data set for which calibrations exist. Figure 1 displays the SIX dispersive doppler calibra- tions (*) and the mean and one-sigma values as obtained from a 20-point running average through the calibrations. Note that the vertical scale is in millihertz, and; as indicated, the noise of the S/X calibration is about 2 mHz on this day. This is typical of the noise characteristics for the pre-Mercury I S/X dual frequency doppler. Figure 2a shows the noise characteristics for a typical day in the superior conjunction phase of the MVM'73 mission. Note, however, that the vertical scale is in hertz and the noise characteristics for this day are, therefore, at least two orders of magnitude larger than those on the pre-Mercury I days. It is also evident that the amplitude of the S/X doppler noise is not stationary. Figure 2b shows the March 24 pass plotted on the one-hertz scale. Figure 3 displays the noise characteristics of the S/X dispersive doppler charged-particle calibrations for a few days between March 24 and June 7, 1974. Note that the scatter increases as the SEP angle decreases (Fig. 4). 48 III. Demonstration That the Superior Conjunction S/X Doppler Calibration Is No Reflection on Charged Particles Figures 5, 6, and 7 display the unedited S- and X-band doppler residuals after the removal of the effects of the spacecraft trajectory and Earth's troposphere. Figure 8 shows the ratio of the noise of the X-band to that of the S-band residuals. Again these ratios have been obtained by 20-point running averages. For significant fractions of these passes, these ratios of the rms noises are larger than four. This is an important observation. The S/X experi- ment, as configured for Mariner 10, has only an &band uplink capability. The X-band downlink retransmitted by the spacecraft is obtained by multiplying the S-band uplink by 880/221 (approximately a factor of 4). The charged-particle effect on the X-band is approximately 1/16 that of the S-band. Consequently, even if there is no charged-particle effect on the S-band downlink signal, the ratios as computed should be at most four. In other words, considering only plasma-ir+.duced noise, the relative rms noise of the X- and S-band dopplers transmitted from the spacecraft is 4 to 1, and, if the downlink S-band doppler is further scintillated by plasma dynamics, the ratio decreases. Thus, it is obvious that the high frequency variations of the dopplers are not due to eharged-particle content fluctuations. The following analysis again confirms that the "charged- particle" calibrations derived from the superior conjunc- tion S/X dispersive doppler data do not accurately reflect the line-of-sight charged-particle dynamics. Figures 9, 10, and 11 show the S-band tracking doppler residuals before and after the application of the calibrations. The &band residuals are of the order of 100 mHz, except for the June 7 pass when they are as large as 200 mHz. However, without exception, they become significantly larger after calibrations. This demonstrates that the S/X calibrations of the superior conjunction phase quality cannot remove the charged particle effect. In fact, noise has been added to the doppler residuals;a noise which is not stationary. IV. Orbit Determination Results Since the calibrations derived from the S/X dispersive doppler data do not accurately reflect the line-of-sight charged-particle effects, when they are applied to the orbit determination process, unreasonable results are obtained. Fig-are 12 shows the OD results for the "state only" solution with and without calibrations. Whereas the uncalibrated B-plane solution is fairly close to the pre- TCM5 current best estimate (B •H - 24,000 km, B •T L- -24,050 km), the calibrated estimate is displaced from the JPL DEEP SPACE NETWORK PROGRESS REPORT 42.25 l =k . B•R values by approximately 10,000 km. The sum of squares of the after-the-fit doppler residuals is increased by almost a factor of 20 when calibrations are applied. As illustrated in Figs. 9, 10, and 11, the calibrations have degraded the S=band residuals by imparting to them the large noise signatures that are in the S/X dispersive doppler data. V. Status on the Investigation of Possible Noise Origins The rms noise of S-band doppler increases dramatically as the SEP angle of the probe decreases (Fig. 13) below 10 deg. Similar behavior was observed in the Mariner 10 (Fig. 13), Mariner 9 (Fig. 13), Mariners B and 7 (Ref. 2), and in the Pioneer 10 and 11 (Fig. 13) S-band doppler data. D. O. Muhleman (Ref. 3) computed the rms phase jitter of S=band frequency transmissions from plasma amplitude scintillation observations and scintillation theory.. The curve containing the shaded area (Fig. 13) is the theoretical rams noise as a function of SEP angle computed by Muhleman. The S-band doppler rms observed is 5- to 6-fold greater than the rms predicted if the SEP angle region of ±3 deg is excluded from consideration: It is an order of magnitude greater than that predicted in the t3-deg zone. One possible explanation for this is suggested from the knowledge that spacecraft radio tracking systems employ "second-order phase-locked loops" (Ref. 4). Such loops require less than it/2-rad phase jitter in the pass bands (Ref. 3) if they are to remain in "uninterrupted" phase lock. That is, the signal received by such a system must have coherence for time scales on the order of a second. w/2 rad of phase shift at S-band frequencies amounts to approximately 3.5 cm. A change in the total electron content along the ray path of 5 X 1015 electrons/m2 is required. Variations of electron content far larger than these have been observed (Ref. 5). It is reasonable to assume that electron content dynamics larger than 5 x 1015 electrons/mQ/s were encountered by the Mariner 10 radio metric doppler. When such dynamics are encoun- tered by a radio signal at S-band frequencies, the domain of linear performance of the radio tracking system may be exceeded. Note further that the doppler noise shown in Fig. 13 is roughly consistent with the 3.5-cm short-term instability. The X-band transmission leaving the spacecraft is obtained by multiplying the spacecraft-received S-band by 880/221. Since this is an exact process, this X-band transmission has approximately 4 times the phase jitter of the S-band transmission. If the spacecraft-tracked S-band doppler contains cycle slips, then the spacecraft-transmit- ted X-band doppler may exceed the linear performance domain of ground receivers. How a "linear receiving system" responds to such S- or X-band signals with such spectral characteristics may be shown: (1) Theoretically by studying the "mathematical model of second-order loops" and how they respond to real and simulated data of the type encountered during the Mariner 10 superior conjunction: (2) Empirically by passing wide-band doppler through the DSS 14 Block 4 receiver. VI. Conclusion Our experience with the S/X dual-frequency doppler demonstration for the pre-Mercury I phase was very promising. For the superior conjunction period of the mission, during which the charged-particle activities are very high, the X-band downlink only configuration is incapable of providing meaningful charged-particle calibrations. JPL DEEP SPACE NETWORK PROGRESS REPORT 42.25 49 'r . i ' I ,i References 1. Winn, F. B., Yip, K. W., and Reinhold, S. J., "DSN-MVM'73 S/X Dual- Frequency Doppler Demonstration," in The Deep Space Network Progress Report 42-22, pp. 28-50, Jet Propulsion Laboratory, Pasadena, Calif., Aug. 15, 1979, 2. Esposito, P. B., Helios-Investigation of the Solar Corona and Relativistic Time Delays During Superior Conjunction, TM 391-478, Aug. 22, 1973 (JPL internal document). 3. Proceedings of the Conference on Experimental Tests of Gravitation Theories, California Institute of Technology, Pasadena, Calif., No ,,. 1970. 1 Telecommunication System Design Techniques Handbook, Technical Memo- randum 33-571, Jet Propulsion Laboratory, Pasadena, Calif., July 15, 1972. 5. Brandt, J. C., Introduction to the Solar Wind, pp. 133=134, W. H. Freeman and Co., 1970. E et 50 xE Z O ae JQU 6 I E I I I I I 4 * la MEAN * % a — * * .* *_ * * *. .2 * - l:r * * * * .4.. MOVING 20-POINT AVERAGE USED TO COMPUTE MEANS AND STANDARD DEVIATIONS. EACH POINT (*} IS A 300-s "COUNT TIME' CALIBRATION .8 —- __ I I.- 13 M 15 16 17 l8 19 20 21 G, ! - (MAR 24, 1974), h Fig. 1. Typical SIX dual doppier, charged-particle calibrations, and associated noise characteristics for the pre-Mercury I phase 0,8 0.6 0.4 0.2 0 H Z -0.2 O m -0.4 V -0.6 -0.8 GMT (MAY 27, 1974), h 0.21 1 r. 0 1 .. v -0.2 15 .... 16 17 18 19 _ .. .. 20 21 22 23 GMT (MAR 24, 1974), h Fig. 2. Comparison of SIX dual doppler, charged -particle calibrations, and associated noise I characteristics for the pre-Mercury 1 phase and superior conjunction phase JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 51 I I ^ I I ^ I 1 0 _l. -1 i 0 -1 MAR 24, 1974 SEP = 30° MAR 31, 1474 SEP = 27° APR 10, 1974 SEP = 22° Z 0 O -% iQ m a V 0 -1 2 1 0 _1 2 2 1 0 I APR 24, 1974 SEP= 15° 0 MAY 3, 1974 SEP=11° MAY -27, 1974 * * SEP=3° JUN 3, 1974 SEP =2' s JUN 7, 1974 SEP = 20 s-^ * 1A 15 1A 17 la 19 20 21 22 23 21 GMT, h * CALIBRATION 1 a NOISE FROM 20-POINT RUNNING AVERAGE Fig. 3. Noise characteristics of SIX dual doppler charged -particle calibrations 52 JPL DEEP SPACE NETWORK[ PROGRESS REPORT 42-25 25 20 15 $, v W 10 5 i s s p K 1,6 I T^ 1' 5 \\ \ 1.4 SEP\\ NOISE ).3-\\ 1.2, \ 0 -J * _ r 16 22 31 6 12 IS 24 30 6 12 18 24 30 5 11 17 23 MARCH 1974 APRIL MAY JUNE Fig. a. Noise in S/X doppler calibrations vs SEP angle 1 0JQ v W a p -i 15 16 17 18 GMT, h Fig. 5. S• and X-band doppler residuals for May JPL. DEEP SPACE NETWORK PROGRESS REPORT i- I 1 I ! 1 'k I ! I * S-SAND * X-BAND 1 ** * t%* x iR a O w O X w U' qae 7 • S-BAND * X=BAND * A * * ** * ** * * FO u 0 ^L. -1 -2 a a 4 o -3 -4 -5 * # # ** # * * * # ** * * # 14 13 16 17 18 6 5 • 416 • • • 3 2 ^ ^ 1 MAY 27, 1974 0 -.._ 1 1 1 -- 1 - 1 y JUN 3, 1974 I ^ • ` • i • Its I 7 5 6 j^ JUN 7, 1974 4 3 14 15 16 17 18 19 20 21 22 23 24 GMT, h Fig. 8. Ratio of X-band to S-band doppler residual noise 1.0 0.8 wr oo Oren 0.6 F4 • 5-BAND # X-BAND # # * ## * GMT, h 0.4 0,2 Fig. 7. S- and X-band doppler residuals for June 7, 19.74 a t 0 z -0.2 cp -0.4 -0.6 -0.8 -1.0 GMT, h Fig. 9. Calibrated and uncalibrated S-band tracking doppler residuals {after the fit} for May 27,1974 17000 19000 E m 21000 GMT, h Fig. 10. Calibrated and uncalibrated S-band tracking doppler residuals (after the fit) for .tune 3, 1974 23000 4 25000 1.0 0.s H 0.6 1.a 0. s a' 0.4 0 0.2 n 0 it p -0.2 —0.4 —0.6 —0.8 ^B , T = —906 km n B , T =511 km 27000 Fig. 12. Pre-TCM5 MVM'73 Mercury II encounter plane coordinate estimates: impact of superior conjunction S/X calibrations l.6 MM '71 GMT, h 1.2 Fig. 11. Calibrated and uncalibrated S•band tracking doppler 7- 1.0 € residuals (after the fit) for June 7, 1974 - w 0.6 0.4 b 0 0.2 R Fig. 13. Rms noise of S-band doppler vs SEP angle x 0.4 0,2 0 l 0 p —0.2 Z -0.4 -0.6 -0.8 —1.0 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 55 s f Non-ionizing Radiation Hazards With the High-Power X-Band Transmitter R. B. Kolbly R. F. Systems Development Section This article describes the results of a survey made to determine if any personnel hazard due to non-ionizing (microwave) radiaticn, would be present when operating the 400-kW X-band transmitter at the Mars (DSS 14) station. This survey showed no significant hazards due to non-ionizing radiation. I. Introduction Traditionally, any time a DSN station is reconfigured in such a manner as to change its power output, operating frequency, or microwave configuration that in turn may alter its radiation pattern, a survey is conducted to determine if any personnel hazards are present. The Developmental Support Croup, Section 335, has, in general, been responsible for these measurements. Although the normally accepted level of non-ionizing radiation for safety is 10 mW/cm 2 (Ref. 1), there is some argument in favor of a lower power density standard for normal working conditions. JPL, has used a power density of 1.0 mW/cmg as a working limit for personnel safety (Ref. 2). In preparation for the MJS'77 mission, a 400-kW X-band (8495 MHz) CW radar has been installed on the DSS 14 64-m antenna. This radar is to determine the structure of the rings of Saturn in preparation for spacecraft encounter. This high-power radar installation represents a significant extension of the capabilities of DSS 14, and previous experience with high-power X-band operation of the DSS 13 100-kW X-band transmitter on the 9-m antenna has indicated a possibility of hazardous radiation levels (Ref. 3). II. Procedure Since this survey was conducted for the sole purpose of determining if any personnel hazards exist due to non- ionizing radiation, an isotropic survey probe was used. Although other techniques, such as a power meter and standard gain horn, are more sensitive than the isotropic probes, the standard gain horn tended to give readings 6 to 10 dB lower. This is because the stray radiation from an antenna does not, in general, present a plane wavefront to the signal gain horn. The isotropic probe has a much smaller aperture so the phase error across the measure- ment aperture is not significant. 56 JPL DEEP SPACE NETWORK PROGRESS REPORT 42--25 The Narda Model 8315 power density meter and the Narda Model 8321 isotropic probe were used to conduct this survey. The minimum detectable signal with these instruments is approximately 0.1 m W /em 2, giving a safety factor of 10 over the minimum hazard level. The Narda instruments have a history of reliability, and their usage is approved by the JPL Safety Office. In addition; two instruments were used in some instances as a cross-check. A catastrophic failure of one instrument (not due to a fault within the instrument) prevented complete redundancy throughout this survey. This survey was conducted in two parts, The first part was with the antenna in the stowed (zenith) position, and a survey of work locations, both on the antenna and at the station in general, was made. Also, normally used access routes (ladders, stairways, sidewalks, etc.) were searched for possible hazards, The second part of this survey was conducted with the antenna in several positions represent- ing beginning, mid-point, and end of a Saturn track (planet rise, meridian crossing, and set). During the second part of this survey, no checks were made of the antenna stricture itself. Ill. Results The results of the first part of the survey with the antenna in its stowed (zenith) position are shown in Table i. The areas in excess of 1.0 mW/cm 2 are confined to the Module III area of the cone. This is the area immediately below the feed cones and is primarily used for receiver equipment. These "hot spots" are associated in all cases with hatches and doorways. All areas below the surface of the antenna were "cold," and no hazardous spots were detected. Table 2 gives the observed data of that portion of the survey with the antenna in typical Saturn tracking positions. The significant feature is the lack of stray microwave radiation. At the conclusion of this test, the antenna was raised to zenith with the probe held in one spot to determine if spill-over or hyperboloid/quadripod scatter could cause a radiation hazard. No significant signals were detected during this test. IV. Conclusions Based on the data in Tables I and 2, the operation of an X-band 400-kW transmitter on the DSS 14 64-m antenna will not result in any hazard to personnel if personnel are restricted to areas below the antenna surface during high- power operations. By more effectively sealing the hatches and doors in the Module III area, it would be possible to allow personnel to work in the Module II and III areas without hazard during high-power X-band radiation. References 1. Safety Level of Electromagnetic Radiation with Respect to Personnel, USAS C95.1-1966, United States of America Standards Institute, 1966. 2. Radiation Precautions in the Deep Space Instrumentation Facilities, EPD- 108, Aug. 1, 1962 (JPL internal document). 3. Kolbly, R. B., Non-lonizing Radiation Hazard Survey at Venus 9 Meter Antenna, IOM 3350-71-060, Oct. 15, 1971 (JPL internal document). JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 57 ,1 Table 1. DSS 14 radiation survey (antenna at zenith) Transmitter power. Measured value, Expected value Location kW inw/cm=9 mW/ern= Module III area Rightaccess door 100 0.1 0.3 Left access door 100 0.3 0.9 XKR cone acces. hatch 200 2.0 3.0 SNIT cone :recess hatch 150 0.8 1.6 Room area in general 150 C0.1 0.1 RF connector at nVT 150 1.5 1'51` Hatch near hamionie falter ( unused) 200 5.0 7.5 Central hub area ( overhead) iUU 0.7 0.7 .Module 11 area Transmitter bay doors 3(}{) 0.2 0.27 Room work areas (overali) 300 <0.1 <0.I Hub area Surface access door 300 0.1 (1.1 Ladder area 180 {0.1 -1.0.1 Lower hub area 300 "'..0.1 <' 0.1 Elevation axis catwalk 300 r,: 0.1 <()A Elevation hearing platform 300 !:0.1 C0A Stairway above clef ation bearing* 300 <0.1 CO31 Elevation drive platform 300 <0. I x:0.1 Lower elevation drive platfonn 500 <0.1 <0.1 Filter house area 300 <0-1 <'O.I Azimuth platform 300 <0.1 '-:0.1 .' IMI- cnnrgrc-ssor area 300 <().1 <:0.1 Stairway to ground 300 <0, I _0,1 Walkway to control building 300 C0.1 <0-1 Control rown 300 C(!.1 <03 Butler building; genend area 300 C0.1 <0.1 Generatorbuilding (C,-81) 300 <()A `0.1 'Not a function of transmitter power- s JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 ^fi Table 2. DSS 14 radiation survey (tracking positions), Saturn rise Saturn meridian crossing Saturn set (Az 84.0 , El = 10.5 }. (Az = 180.0 , El - 76.0` ), (Az 282.0 , El 10.8' 1 Location nAV/cm^ 111W/cm-, MW /cm-, DSS 14 control room <0.1 C0.1 <0.1 Walkway to 64-m antenna <0.1 C0.1 <01 64 -m antenna chain perinletor <0. l <0.I <(). I Directly helow disk lip 0.10 <03 0.12 Step to heat exchanger 0.1 5 <0.1 <0.1. 30 m ( 100 ft) an dish axis <0.1 <0.1 C().1 15 in (50 ft) cast of C-83 beat exchanger 0.113 <0.1 <0.1 Building G-82 <0.I <0.1 <0.1 y1G Set and G-82 area <0.1 <0.1 <0.1 West wind tower <0.1 <0.1 C0.1 C-81 ( power house) <0.1 C01 C 0.1 SSE Butler building <0.1 <0.1 <0.1 Front of control building <0.1 <0.1 <0.1 Road to guard sta : n <().1 <(). I <0.1 Guard station <0.1 <0.1 <0.1 Road to roar of control room <0.1 <0.1 <0.1 West surticy marker plate antenna p11111be test (Az 282.0 _ 10.8 6 -0-09 -1.09 -0.45 -0.64 50 688.17 - 15.09 -14.79 -0.50 -0.02 0-59 -.0.61 60 689.00 -12.23 --11.38 - 0.85 +1.19 1.71 -0.52 70 689.83 -- 8.27 - 6-M -1.861 - 2.68 W-- 80 690.61 -- 4.32 - 1.31 -101 2.97 3.44 --0.47 90 691.50 0.16 7.51 -2.41 148 3.95 0.47 100 692.33 2.34 5.15 -2,81 3.77 4.72 _0.45 110 69+3.17 4.21 6.63 -2.42 3.113 4.23 11,4(] 120 694.00 5.15 7.20 -1.75 3.65 4.01 036 130 694.83 5.10 6.93 -1.83 3.24 3.53 - 0.29 140 695.67 4.39 5.76 -1-47 ---- 2.81 - 150 696.-0 2.14 3.48 -1.34 1.54 1.86 --0,32 160 697.33 - 1.79 - 0.14 -1.65 0.37 0.76 -0.39 170 698.117 - 6.43 - 4.96 ---1.47 ---- - 0-31 -- 180 699.10 -10.7.1 - 9.42 ..1.32 -- -0,99 - aCalcalated standard error on the measured relative range was typically -0.5 ns "Based on A = 0.297 { 10.55 dB) 72 JPL DEEP SPACE NETWORK PROGRESS REPORT 4225 r.; iis r:. N REFLECTOR Ile _ _ry^ UPLINK PRIMARY PATH Dowl PORT 0 GROUND RECEIVER Fig. 1. Geometry for analysis i SPACECRAFT RADIO OR ZERO DELAY DEVICE GROUND TRANSMITTER DIPILEXER JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 mO a Z L5 r a 3 O ^ 3 6 3 c o Z G aa U -2 r _s -E i 3060 3050 s100 3-I 3700 31 0 3366 DIFFERENTIAL PATH LENGTH, c, Fig. 2. Two-way range error sample case: 1 -' — 11 = 3048 cm (100 ft); one-way leakage signal is — 30 dB relative to primary signal; uplink signal is 2-113 MHz, and downlink signal is 2295 MHz;L„=: j =0 H VVI fit 0 -It 1 _4 1-1 H 1i I i : i A A 11 -11-1-1 O -1s -25 3DW 3050 3!00 :115n 3200 'V G 3300 DIFFERENTIAL PATH LENGTH, cm Fig. 4. Two-way range error sample case: same parameters as Fig. 2 except leakage signal is —20 dB relative to primary signal 2.0 1.5 !.6 v O a.s i a0 z Q 3 -1.0 Jn00 3050 31 GC 3`5{1 3?00 ':iC f 01F-_2E n1TIAt PAPILENGTH, cm. Fig. 5. Two-way signal level error sample case: same parameters as Fig. 2 except leakage signal is —20 dB relative to primary signal JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 I - i 50 3200 9250 3300 a0 w z aoc d v a 3 Y a w J J Q zL N Q3 O3 j { 0- II1 I 2 DIFFERENTIAL PATH LENGTH, cm Fig. 6. Two-way range error sample case: same parameters as Fig. 2 except leakage signal is —10 dB relative to primary signal • r 4 1 , V DIFFERENTIAL PATH LENGTH, cm Fig. 7. Two-way signal level error sample case: same parameters as Fig. 2 except leakage signal is —10 dB relative to primary signal 76 JPL DEEP SPACE NETWORK PROGRESS REPORT 42.25 0a Z aa a3 0O 3 5 WJ W ,sl J J QZ Vf YQ d 3r i { 6 8 3040 3060 3060 3100 3120 31-10 3160 DIFFERENTIAL PATH LENGTH, cm Fig. 8. Two-way range error sample case: 1, — 11 = 3048 cm (100 (t); one-way leakage signal is —30 dB relative to primary signal; uplink signal is 2113 MHz, and downlink signal is 8415 MHz; Y,,=4,j =0 DIFFERENTIAL PATH LENGTH, cm Fig. 9. Two-way signal level error sample case (same parameters as Fig. S) 11'[. DEEP SPACE NETWORK PROGRESS REPORT 42-23 71 .: axY w 0 Zax a} O 21 1 —2 _2 78 2.0 1.5 1.0 0 it a.s Z N} a -o.s3 43 ~ 1.0 -1.5 -2.0 Fig, eten sign, DIFFERENTIAL PATH LENGTH, cm Fig. 10. Two-way range error sample case: same parameters as Fig. 8 except leakage signal is —20 dB relative to primary signal Ua z a y a3 O r av 40 . . ICA — I 20 o I i 20 I 40 i -60 .. 80 00 3040 3060 3080 3100 3120 3140 316n DIFFERENTIAL PATH LENGTH, cm Fig, 12. Two-way range error sample case: same parameters as Fig. 8 except leakage signal Is —10 dB relative to primary signal 11 lilt IIII 11111 11111 11111 c i V 8 3040 3060 3060 3100 3120 314C 7160 19 0 W JW7 J a Z N ^y y}T W DIFFERENTIAL PATH LENGTH, cm Fig. 13. Two-way signal level error sample case: same param- eters as Fig. 8 except leakage signal is —10 dB relative to primary signal !PL DEEP SPACE NETWORK PROGRESS REPORT 42-25 79 80 JP RANGE-CODED 2113-MHz UPLINK BLOCK 111 MULTIPATH EXCITER DEVICE RANGE-CODED 516 kHz RANGE-CODED 2113-MHz UPLINK22 MHz RANGE CODE 211.3-MI1z AND Hx DOWNLINK DOWNLINK LINK PROOF TEST MU-1 10 MHz BLHz-BLOCK III MODELRANGNGI RECEIVER MVM'73 RADIOMACH NE FREQUENCY SUBSYSTEM IN-PHASE^UADRATURE CORRELATION CORRELATION SDS 920 OUTPUT COMPUTER DATA Fig. E4. Measurement setup for two-way range tests with the muitipath device 1 i Appendix A Upper and Lower Bounds for Two-Way Range Error As can be seen from the sarnple case blots (Figs. 2 IF,,,h,, 40log,,,(1 A) (A-7). to 13), the error for two-way range will be at a local upper or lower bound when the modulation envelope is These upper bounds of error for two-way range and at a maximum or minimum. At some critical differential signal level Luc c^actly hviec those of the corresponding length, the two-way range: error will be exactly one-way range case (Ref. 1). To find the critical differ- t%vo times the upper or lover hound of the one.-way ential path length which produces these conditions, first range error (Ref. 1). To find where.. this condition occurs, substitute Eq. (A-5) into (A-I) to obtain let B„ and B F, as given by Eqs. (5) and (6) be related as follows Bz = - 1 (m -- k) (A-8) Then substitutions of Eqs. (5) and (6) into Eqs. (A-5) and (A-8), respectively, and sol ving for 1_ 1, results in where k is a positive integer. Then the two-way range error given by Eq. (2) becomes ( C 2A co.s 0,, - A 2 ) (A-2) c [)n -4 k 01, 1.2-2,.\ A - cos B„ f' L 2V Also note that the two-way signal level error as given by Eq. (8) becomes For simplicity assume that there is only one reflection coefficient in the leakage path and d,,, _ 4,, =- v. Then ^F" = 20.log,,, [1 +2A cos B„ + A=] equating Eq. (A-9) to Eq. (A-10i and manipulation re- (A-3) From Eq. (A-3), it can be seem that the peak-to-peak chance in signal .level will be 1A,,,, = pia Ing,,, I -- A^I (A-4) which is exactly a factor of two greater than the dB signal level ripple for the one-way case (Ref. 1). Upper Bound Assuming that the conditions of Eq. (A-1) exist, then assume further that cults ,n 2 (in k) I -11 The condition of Eq.. (A-I.1) Faust be fulfilled if two-Nvav range error is exactly twice the one-dray range value. To show a practical application of Eq, (A-11), one can find from trial and error that rn = 11. and k 1. are the minimurn values of rn and k which will give fh ^_-: 295 11Hz when f„ = 2113 MHz. From substitution of these values in Eqs. (A-11) and (A-9) A:- 2296 t 11Hz I, ._. 1, -- 163.3 cm (5.36 ft) B„ — 2-r m (A-5) where ,n is n positive integer. Substitution of Eq. (A-5) into Eqs. (A-2) and (A-3) gives ?A 1, 1, JPL DEEP SPACE NETWORK PROGRESS REPORT 42.25 and from Eq, (A-6) (E,)T = 10.89 A1 ... 1 where (eg),, is given in nanoseconds. ^J Lower Bound To find where the two-way lower hound is exactly twice the one-way lower hound, assume that the condi- tion -of Eq. (A-1) exists, and assume further that B,= = —(2n — 1)7r (A-12) where n is a positive integer. Then Eqs. (A-2) and (A-3) become (EV)r = — r 1 2At^ \ ^ , L 1 (A-13) ) Fr j ,1, = 40 log,,, [1 -- A] (A-1411 To find the differential path length which produces these lon=er bounds, substitute Eq. (A-12) into Eq. (A-1). to obtain 8b ^ — (2n — 1)ar — 2rrk (A-15) Then substitutions of Eqs. (5) and (6) into Eqs. (.A-12) and (A-15), respectively, and then solving for L, -- k, re- sults in f= ^ n ^- 1 ^ + 1-16 C2n—I ?k)+ °^ (A17) rr Assuming that 4'u = ^b = 7r and than from equating Eq. (A-16) to Eq. (A-17), one obtains A = f. I re n k ^ (A-18} As an example of the use of Eq. (A-18) one can find from trial and error that values of n = 23 and k = 2 will give fu ^- 2295 MHz when fa = 2113 MHz. From substitutions of these values into Eqs. (A-18) and (A-16), one obtains A — 2296.7 MHz k, = 326.5 cm (10.71 ft) and from Eq. (A-13): ( Er)T = — 21 .77 A1 --A 1 where (F,,), is given in nanoseconds. Although in the examples given, the calculated down- link frequency of 2296.7 MFjz is only approximately equal to 2295 N111z, one can expect to find local upper and lower bounds at differential path lengths close to 163.3 cm (5.36 ft) and 326.5 cm (10.71 ft). It is of interest to note tbaL even for these small differential path length values, significant error in the S-hand two-way range will occur if the multipath signal is strong. This type of strong multipath effect for small differential path lengths on the \IVM' i3 spacecraft was pointed out by J. R. Smith (Ref. 3). Acknowledgments The experimental work at the Telecommunications Development Laboratory was supborted by D. L. Brunn of the Spacecraft Radio Section. The computer program for the sample case plots in this artivle was written by T. Cullen of the Communications Elements Research Section. References 1. Otoshi, T. X., "S/,X Band Experiment: A Study of the Effects of Multipath on Group Delay," in The Deep Space Network Progress Report 42-24, pp. 40-54, Pasadena, Calif., Dec. 15, 1974- 2. Smith, J. R., "Viking Ranging Investigation Tewn," 1041 338,2 74-076, July 30, 1974 (JPL internal document)_ 3. Smith, J. R., "Viking Ranging Investigation Team," 10-M 3382-74-102, Oct. 15, 1974 (JPL internal document). JPL DEEP SPACE NETWORK PROGRESS REPORT 42-2. Maximum Likelihood vs Threshold Frame Synchronisation B. K. Levitt Communications Systems Research Section Mariner 10 (AIVAI'73) uses a threshold-type algorithm to acquire frame syn- chro ►tization. In reviewing this scheme, the question arose as to ashy a threshold approach was selected over a maximum likelihood detection scheme. This paper ansccers that question in the context of an uncoded telemetry link over a binary symmetric channel. For a given communication link it is demonstrated that, at the expense of a variable acquisition tune, a threshold scheme can simultaneously achieve a Io.wer probability of false sync acquisition and a smaller expected acqui- sition time than its maximum likelihood counterpart. 1. The Problem In a binary signaling scheme, frame synchronization is usually provided by prefixing each frame of transmitted data (.11 bits) with a fired binary pattern or sync word (L bits). At the receiver, frame synchronization is ac- quired by locating the noisy replicas of the transmitted sync words periodically imbedded in the received data stream. Suppose we are dealing with. uncoded data received over a binary symmetric channel (crossover-probability E): the optimum frame sync decision is then based on the Hamming distance metric. In particular, we examine successive binary L-tuples p,,p_, • • • within the received bit stream (see Fig. 1): we know that one of the first Al such L-tuples must be received sync word.pm*_ Siatistic- ally, m* is uniformly distributed over (1,M). To compare these received L-tuples with the sync ward pattern s, we form the likelihood parameters D,,D_, - • • , where D. is the Hamming distance between p,,, and s. Typically, D.. will be near 0, while the other (111-1) parameters Dm within a frame of received data will be near L/2 (assume s is a Barker (Ref. 1) or Neuman-Hofman (Ref. 2) se- quence, and the (]11-L) information bits in each frame of transmitted data are independent, equally likely 1's. and 0's). Xi'e acquire frame synchronization by correctly iden- tifying rn* over (1,4%f): this is a detection problem with mane solutions, some of which are discussed below. 11. Some Solutions Suppose we are constrained to make a. sync decision over a single frame of received data. Then the optimum maximum likelihood (AfL) approach is to decide m` = m if D,=min(D.:m=1.2,•••,M) (1) The advantage of such a scheme is that the sync acquisi- tion time is deterministic: assuming a unique minimum exists, we are guaranteed a sync decision will be made 84 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 after observing one frame of received data. On the other hand, if Do is not particularly close to zero, we are still forced to make a sync decision, even though our confi- dence in that decision is low. Thus; if the bit error proba- biiity E is too large, the ML scheme may have an unac- ceptably large probability of false sync acquisition, Pr[FS]. We can improve Pr[FS] by making a joint ML sync decision over more than one frame of received data (say, N frames): thus we can decide m* = ni if N-1 J'-1 ED,^,„ky = min E D„,.k„: m = 1,2, .. •, M (2) k=o k=o The averaging over several frames of received data im- plied by the summation in Eq. (2) provides a degree of noise immunity and results in a significant decrease in Pr [FS ] . However, our sync acquisition time is now N frames of received data, and our storage requirements are increased proportionally. An alternative approach is to delay making a sync decision until we are reasonably confident it is correct. To this end, we can successively compare D 1:D,, etc., with some predetermined threshold T: we decide that P^ is a received sync word if D„ is the first metric to satisfy the threshold test D,,, C T (3) The selection of the threshold T involves a tradeoff between frame sync reliability and acquisition time. Clearly, Pr[FS] decreases as T gets smaller. However, if T is too smal1, we may not recognize the first few re- ceived sync words due to excessive (T + 1 or more) bit errors within them: then the sync acquisition time (now a random variable) may be several frames of received data. Note that if the first received sync word p , k is the first received L-tuple to satisfy the threshold test, the corre- sponding acquisition time is m*/Af frames: consequently. the threshold synchronization scheme above has a min irnrim expected acquisition time of m*_ M.+l. frames (4) 31 2111 (assuming a correct sync decision is made). The design criterion for a given telemetry link (fixed AI,L,E) is to select a threshold T for which Pr[FS] is acceptably small and the mean acquisition time is of the order of % frame. As in the maximum likelihood approach, if storage capacity permits, a more reliable sync decision can be made by using a joint threshold test over N frames of received data: determine the first location m which satis- fies the test 3-1 E Dr„kx < T (5) k: o III. Comparison of ML and Threshold Synchronization The maximum likelihood synchronization technique above is optimum, in the sense that it minimizes the probability of false sync acquisition, only tchen the ob- servable is a fixed amount of received data. A threshold scheme can outperform its AfL counterpart operating on the same N-fold Hamming distance metric, .► -k Dui-F.-.k! k it provided the threshold T is properly chosen, at the ex- pense of having a variable acquisition time. The general hypothesis is that for any E,E1i,L, and N, there exists a T such that the Pr[FS] and the mean acqui- sition time will both be smaller than in the ML case. I am not prepared to prove this general statement, however, it is shown to hold below, in the particular case N = 1. X11 = 7056, and L = 31. (This combination of Af and L corresponds to the Mariner 10 high-rate video telemetry mode, which was of interest during; my initial investiga- tion of the frame sync problem.) Using union bounding techniques, one can derive upper bounds for the probability of false sync acquisition for the ML scheme of Eq. (1) and the threshold approach of Eq. (3) . (derivations are similar to the appendix of Ref- 3): Pr[FS] < ML L k ;.1f - 112 t(1 —E11 k) (T"_E)' E(L) (6) Pr[FS] < T T Of ---1.12. F.. k ^^ L min(A,B)Lk-o k} + 1—A (7) 3PL DEEP SPACE NETWORK PROGRESS REPORT 42-25 85 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25aEts f where 7' r: reA. 1 -- (1—e)', L 1—E (8) T B _^ (A1-1) 2- 1 ^ ^L, {9) r =o \ k f For sufficiently small E, these bounds should be fairly tight. The acquisition time is fixed at 1 frame of received data in the AIL scheme. 1n the threshold case, a simple Markov analysis (similar to Section I.I, Appendix, Ref. 3) yields the result — mean acquisition time ^ q^ t/,11+1 -b L-) frames231 1—A (10) provided. Pr[ FS ] I < < I. r The formulas in Eqs. 6-10 were used to generate Figs. and 3. They show that for any vahie of e, a value of T can be found to make the threshold scheme superior to the Al L approach: Pr[FS J G - Pr[FS] (11) AIL mean acquisition time I < I fralne (lo) 1T - 1' or small bit error rates (E < 10-n), the probabilities of false sync acquisition for the f11L and T = 0 threshold schemes are comparable (actually, Pr[FS] ^T=O Pr[FS ); however, there is a factor of 2 advantage I ML for the threshold approach with regard to the mean acquisition time. As E increases from 10 to 10- 2, the mean acquisition time for the T = 0 case rises toward 1 frame; simultaneously, Pr[FS] increases much T=O more slowly than Pr[FS] !, , yielding more than an I ML, order-of-magnitude performance advantage at e = 10 In the region 9.6 X 10- < E < 1.3 X 10-'-,the T = 0 and T = 1 thresholds both satisfy Eqs. (11) and (12); over the range 1.3 X 10- 2 < E < 2.5 x 10 these constraints uniquely require the threshold T = 1, The graphs indi- cate where T must be increased as E increases furener. Of course, the bounds on Pr[FS] become progressively looser as a becomes large. References L Barker, R. H., "Group Synchronization of Binary Digital Systems," Communica- tion Theory, edited by Jackson, Butterworth, London, pp. 273-287, 1953. `?. Neuman, F., and llofrnan, L., -New Pulse Sequences With Desirable Correla- tion Properties," Proc. Nat. 1'elernetry Conf., Washington, D.C., pp. 277-282, Apr. 1971. 3. Levitt, B. K., "Frame Synchronization Performance Analysis for >1IVM73 Un- coded Telemetry Modes," in The Deep Space Network, Technical Report 32-1526, Vol. XTX, pp. 126-136.. Jet Propulsion Laboratory- Pasadena. Calif., Feb. 15,1974. WZ O dUa 1.0 ML. 4= 3.8x10-2 c= 6.6X1.0,2 M = 7056 j 0.4 L = 31 0.8 j II c=1.3x102 i k Ei 0.7 I 0.6 I I T = 0 T 1 yiT= T=3 = 0.5 i . .I TRANSMITTED BI1 .,.AM- M-BIT FRAME --- 0 0 1 1 1 0 0 1 0 1 1 0 _-- 0 1 0 1 1 1 0 0 1 0 1 0 1 L-BiT RANDOM SYNC WORD DATA RECEIVED BIT STREAM (85C): RECEIVED SYNCP2 WORD, p .m --- 0 1 0 1 0 1 1 0 0 0 1 0 1 1--- 0 1 1 1 0 1 0 0 1 0 0 0 1--- P1 Fig. 1. Frame synchronization formats for uncoded transmission over a binary symmetric channel Z 0 afl d Z J a wO a m O S1 a 10 10_3 2 4 7 10 2 4 7 10-1 a _. BIT ERROR PROBABILITY e 10-6 Fig. 3. Comparison of mean acquisition times for threshold 10-3 2 4 7 i0.2 4 7 10-1 and maximum likelihood frame synchronization techniques _ BIT ERROR PROBABILITY [ Fig. 2. Performance comparison of threshold and maximum likelihood frame synchronization techniques 9 - 10 ua, W T=0 P 3 O 1e= 9.6xIC MLm „5 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 87 J jFurther Applications of the Atmospheric Fading Model to Sequential Decoding Performance B. K. Levitt Communications Systems research Section The Deep Space Netteork is interested in predicting whether it will be able to achieve a satisfactory performance level oil Venus 1978 (PV'78) telemetry over a fading channel. In an earlier article, a theoretical model for tl:e combined effects of lob-normal fading and a noisy carrier reference on sequentially decoded phase-shift keyed (PSK) telemetry teas used to analyze the PV'78 large probe link at 256 bps. This model is note applied . to the 16-lips small probe telemetry mode. Introduction An analytical model was recently developed for pre- dicting the combined effects of log-normal fading and a noisy carrier reference on convolutionall.y encoded/ sequentially decoded phase-shift-keyed (PSK) telemetry (Ref_ 1). In a previous article (Ref. 2), this model was used to analyze the Pioneer Venus 1978 (PV78) large probe telemetry link at 256 bps. As part of a continuing DSN support study, a similar examination of the 16-bps small probe telemetry mode is reported here. Assumption As in the 256-bps case, the desired frame deletion rate was set at 10 The received signal -to-Noise ratio P,/A'„ required to achieve this level of performance was com- puted as a function of the severity of the channel fading, characterized by the variance n-t2 of the log-amplitude fluctuations. Using experimental data from the Russian Venera space probes, NVoo (Ref. 3, Eris. 12 and 13) has shown that max" = 0.0142 — (1)ai where L is the atmospheric path length of the probe-to- Earth telemetry link, in kin. The fading/noisy reference model v,,:orporates process- ing losses in the data and carrier tracking channels (Ref. 2, Eqs. 2 and 3); at 16 bps, these anticipated losses are L„ = 2.32 dB (2) L,• = 1.00 dB (3) 88 JPL DEEP SPACE NETWORK PROGRESS REPORT 42:25 It was apain assumed that a standard DSN sequential decoder could perform about 25;000 computations/second in real-time operations; this translates into a computa- tional capacity N = 1562.5 computations/bit at 16 bps. A value of N an order of magnitude larger than this was also used to determine whether a significant improve- ment in performance could be achieved by resorting to non-real-time decoding. As in the 256-hps analysis, we constrained the tracking loop to have a carrier reference phase jitter U O 2 compat- ible with very long baseline interferometry (VLBI) re- quirements. This required that the received carrier signal-to-noise ratio in the (two-sided) threshold phase- locked loop bandwidth 2131,,, satisfy the constraint (Ref. 2, Eq. 4) P,. Cos" 8 w 't — N„213 Lr > (10 + 14.1 (r,') dB (4) where 0 is the modulation angle, and 2131.,, = 12 Hz. Finally, despi f t previously expressed reservations (Ref. 1, "Cotnmentaq,° p, 60; Ref. 2, "Results"), the analysis of the 16-bps link was performed using.Laylan&s formula for the characteristic decoder memory time T,,, (Ref. 4, Eq. 6) in the fading/noisy reference model. There are plans to determine this parameter empirically so as to maximize the agreement between our analytical model and experi- mental evidence. Ill. Results As a reference point for design control table purposes, in order to measure losses due to fading, noisy carrier reference, and receiver processing, an idealized 16-bps link with U, ' = 0, L,, = L{• = 0, and a perfect carrier reference was analyzed. The results are contrasted in Table 1 with the 256-bps case (Ref. 2, Fig. 1) as a function of the decoding rate C. We find that the slower telem- etry link requires a 0.50-dB smaller received bit energy- to-noise ratio p for real-time decoding, with a lesser savings in the non-real-time case. Figure I still neglects the fading, but incorporates the noisy reference and processing losses into the analysis of the 16-bps link with. real-time decoding. Strictly from a telemetry viewpoint, we see that our do-sired frame dele- tion rate of 10 = could be achieved in this case with P,/N„ as low as 22.0.3 dB at a corresponding modulation angle B = 46.8 deg; however, the tracking loop parameter ,t would then he 6.96 dB, which would not satisf y the VLB1 requirement, ,, = 10 dll in the al,seiice of fading. The minimum received signal-to-noise ratio which simul- taneously satisfies the data and carrier channel require- ments is PrIN„ = 23.19 dB at 9 = 31.7 deg, an increase of 1.16 dB over the data requirement alone. Using Fig. I and a similar set of curves for the non-real- time decoding case, the variation of Pr/N„ with B is shown in Fig. 2 for a deletion rate of 10- in the absence of fading. The solid curves indicate the regions where ,j ? 10 dB. The remaining graphs deal with the effects of atmo- spheric fading, which, we have already noted, is charac- terized by o,°. During its approximately 2-hour descent to the surface. of Venus, v, will vary from an initial value of zero to a maximum value on the surface, when the atmospheric path length L in Eq. (1) is greatest. Refer- ring to Fig. 3, suppose the probe-to-Earth transmission angle is q relative to the radial direction; assuming Venus has a radius of 6050 km, and the atmosphere is homo• geneous and ends abruptly 55 km above the surface of Venus (Ref. 5; Ref. 3, p. 8), a transmission froth the surface has an atmospheric path length L = (6105)" — (.6050 sin 60.50 cos p, km (5) Equations (1) and (5) have been combined in Graph 3 to provide a curve of a,^ at the surface of Venus vs the transmission angle 0. Two values of 0 have commonly been used as benchmarks for the PV"78 mission; the corresponding values of a,' from Fig. 4 are {0.014; 0° v^ 1 (6} J0,049; = 60* Figure 5 represents the degradation of the link in Fig. 1 due to log-normal fading, when o:` = 0.049. As before, the optimum operating point with regard to our telem- etry performance requirement only (Pr /N,, = 24.48 dB; 8 = 50.9 deg) does not satisfy the VLBI requirement (-q 10.69 dB). To simultaneously meet both needs, the minimum received Pr/N„ = 24.94 dB (an increase of 0.46 dB, which is less than in the nonfading case of Fig. 1) at 8 41.1°. In analyzing, the 16-bps Iink over the probe lifetime, this represents the worst case requirement for 0 = 60°. . Figure 6 is an extension of Fig. 5 and demonstrates how our link requirements vary with U, = for real-time decoding; Fig. 7 does the same for the non-real-time j.' i y y^ y 4. case. For the 0.049 case, Fig. 7 shows that increas- (minimum of the carrier and data channel margins) is ing the computational capacity an order of magnitude 5.78 dB; this can be compared with an overall margin of lowers the required PrlN„ to 24.79 dB, which is a trivial 2 .45 dB for the equivalent 256-bps link. Note that the savings of 0.15 dB over the real-time decoding require- noisy reference and. fading losses for these two links are meet. virtually identical: As an example, Table 1 and Figs. 2 and 6 were used to 112 dB; 16 bps generate the design control table shown in Table 2 for noisy reference loss — (7) the 16-bps link with o K= = 0A49 and real-time decoding. 2.10 dB; 256 bps The entries for this table are derived in the manner described for the 256-bps link (Ref. 2). Unlike the 256-bps 2.74 dB; TB bps case, the carrier and data channel .margins are equal at fading loss = (8) 16 bps. In the example of Table 2, the overall link margin 2.75 dB; 256 bps References 1. Levitt, B. K:, "Performance Degradation of Vncoded and Sequentially De- coded PSK Systems Due to Log-Normal Fading," in The Deep Space Network Progress Report 42-23, pp. 58-67, jet-Propulsion Laboratory, Pasadena, Calif., Oct. 15,1974. 2. Levitt, B. K., "Pioneer Venus 113'8: Telemetry Performance Predicts," in The Deep . Space Network Progress Report 42-24, Jet Propulsion Laboratory, Pasa- dena, Calif., Dec. 15, 1974: 3. Woo, R.,.et al., Effects of Turbulence in the Atmosphere of Venus on Pioneer _s Venus Radio -- Phase 1, Technical Memorandum 33.644; Jet Propulsion Lab- oratory, Pasadena, Calif., June 30, 1973. 4. Layland, J. W., "A. Model for Sequential Decoding Overflow Due to a Noisy Carrier Reference," in the Proceedings of the International Telemetering Con- N ference (ITC74), held Oct. 15-17. , 1974; Los Angeles, Calif, 5. Yakovlev, O. I., Efinmov, A. 1., and Timofeeva, T. S., "Venera -7 Space-Probe Data on Propagation of Radio Waves Through the Venusian Atmosphere and Through the Interplanetary Plasma," Kosm. Issle, Vol. 9, No. 5, pp. 748 -753, September-October, 1971. 1 } i } 90 JPL DEEP SPACE . NETWORK PROGRESS REPORT 42.2"5x ; a ^ Table 1. Required signal-to-noise ratios for ideal lossless telemetry links at 16 and 256 bps (reference case) No fading ( ati 2 = 0); perfect carrier reference; no system losses (Lo = Lc = 0); Frame deletion rate = 10 -2 Parameter Real-time processing Non-real-timeprocessing C, comp/s 25 x 10+ 2.5 x 105 Ra,bps 16 256 16 256 N = C/R, comp/bit 1562.5 97.7 15,625 977 p - Ea/N,, dB 2.08 2.58 1.77 2.14 Table 2. Telecommunications design control table Telemetry mode: PV'78 small probe-to-earth telemetry link; Convolutional coding (K = 32, v = l%) with sequential decoding; Real-time processing,. N = 1562,5 comp/bit No. Parameter Nominal value, dB Comments Performance - - Transmitter: 10 W1 Avaflable PT/No 30.72 Receiver: 26.1 °K, 30° elev 2 Threshold snr, n 10.00 VLSI requirement 3 Fading lass 0.69 cz= = 0.049 4 System loss; Le 1.00 Carrier 5 2BLO 10.79 12 Hz 6 CO520 -2.46 9 = 411° 7 Required Pr/No 24.941 Nos. (2+3+4+5-6) 8 Margin 5.78 .Nos. (1-7) 9 Ideal p (lossless) 2.08 Deletion rate = 10-2 10 Noisy reference loss 2.12 11 Fading loss 2.74 cX2 = 0.049 Telemetry 12 System loss, Lp 2:32 l 13 hate, It. 12.04 16 bps i 14 sin2B --3.64 a = 41.1° 15 Required P1,1No 24.94 Nos. (9+10+11 +12+13-14) 16 Margin 5.78 Nos. (.1-15 ). L JPh DEEP SPICE NETWORK PROGRESS REPORT 4225 a 91 r _T_ I RB = .16 bps NO FADING 1aX = 0^ 10 dB NOISY CARRIER REFERENCE = 10 dB 1 SYSTEM LOSSES: ' LD = 2.32 dB ' LC = 1. D0 dB 1 FRAME DELETION RATE = 10-2 1 1 1 ,N = 1562.5 comp/64 1 \N = 15625 camp/bit \ \ / 20 30 a0 ..... 50 60 JPL DEEP SPACE NETWORK :PROGRESS.REPORT 42.25. ,:a 23 V 0 za 22 $, deg Fig. 1. Signal -to-noise . requirements for 16-bps telemetry link in the absence. of fading, with real-time decoding B, deg Fig. 2. Signal-to-noise ratios required to achieve a frame deletion rate of : 10-2 in the absence of fading TO EARTH ON F E Fig. 3. Variation of atmospheric path length L with transmission angle 0 from the surface of Venus 4 I^ 1 ti R = 16 b NO FADING(QX = 0) I 0" a2. NOISY CARRIER REFERENCE N = 1562,5 comp/bit • SYSTEM LOSSES: LD = 2.32 dB 1 LC = 1.00 dB S ^^^^, j d D I ^ c* .ate •o aw ^-3 a. a^ 5 1. a a s /Locus OF go r I 1 r 0. 0. i wUa a N X j b 0. 28 1 50 27 . 15 26//FADING PT/No O 40 Z bps 25 62.5 compAir CARRIER REFERENCE LOSSES: = 2.32 dB 24 = 1.0,0 dB TRANSMISSION ANGLE ¢, deg FRAME DELETION RATE = 10 (10 + 14.1 a2) dB Fig. 4. Variation of log- normallading parameter a;= at the surface of Venus with probe transmission angle 23 _ 3(,.0 0.04 0.08 0.12 0.16 X 10-1 Fig. 6. Degradation of' Ira-bps . telemetry link with real-time do-Rs = 15 bps coding as a function of atmospheric fading parameter ox- FADING: cX 0.0496 NOISY CARRIER REFERENCE N = 1562.5 comp/bih 3 4 SYSTEM LOSSES: LD =2.32 dB LC = 1.00 dB 2 ZPT /N0 =24.4 d8 O .1 Q 2. all 24.5 g ` 1t.9 4'8 .1 o¢c 5 \ ZS• 0 f ou Z 7 = 10.59 d8\ a 4 LOCUS OF 110 PT l 2 10-1 37 40 43 46 49 52 11. The Commanding. of Spacecraft Experience over the last decade has shown that a spacecraft's mission is beset with unpredictability, targets of opportunity, and extensions to the prime mission which are most easily handled by remote control. The ground- 3 based command system presented in this report imphe- -47 A i A Multiple-Rate Command System R. F. Emerson Communications Systems Research Section The impact of a.multiple=rate command capability on the present end-to-end ground spacecraft command system has been studied. Limitations in the present command system include a maximum average command word (7I bits or less) transfer rate of 1 word per second and a mean time between failure of 23 hours for the.ground . portion of the system. Command rates are currently set by-end-of- mission (EOM) requirements. Adding a multiple-rate command capability to the present spacecraft command subsystem would result in more reliable flight computer updates during mission phases which could support higher than EOM command rates. During non-catastrophic spacecraft anomalies, commanding could be made more reliable by decreasing the command data rate below EOM requirements. In addition, a flexibility of command rate could be used to optimally apportion command activity between the 26-m and 64-m antenna Deep Space Stations when multiple-spacecraft missions are in progress. The increase in hardware cost necessary to implement a multiple-rate command capability is estimated to be less than 3% of that of current command flight hardware. 1. Introductibn This report describes the results of an investigation into the overall ground/ spacecraft command system. The investigation was directed to increasing the ability of the command system. by .incorporating'.a' multi le rate capabil- ity. The present command system with its capabilities and limitations is outlined. This is followed by a discussion of the impact and benefits which a multiple-rate requirement W. ould have on the system. The impact. is shown to be small, but the return in improved utilization would permit r f. greater command traffic and complexity at less cost than the present system expanded to . meet the.. same require- ments of traffic and complexity. JP! DEEP. SPACE NETWORK'. PROGRESS . REPORT . 42-25. R X95 i:.-rr ments this remote control and thus provides for optimum use of the spacecraft in flight. By combining the technical expertise, data processing power, and decision making capabilities of a ground support team with a reliable and efficient command link, both the operation of the spacecraft and the usefulness of data returned by the spacecraft are improved. An overall view of the present system is provided to furnish a base for the discussion of one improvement in the system; specifically, the capabil- ity of commanding a spacecraft at any of several predetermined bit rates consistent with performance requirements and mission phase. Unmanned planetary missions in the past and through Mariner Jupiter/Saturn 1977 (MJS'77) have not had a major requirement for more than one command bit rate. This, however, is not the case starting with Mariner Jupiter/Uranus 1976 (MJU'79). The third section addresses some solutions to this requirement. The advantages of this improvement, called a Multiple-Rate Command System (MRCS), extend beyond the requirements of the MJU'79 mission. An MRCS would provide improvements in the overall reliability and operations costs on all missions. III. The Present Command System The present command system is a combination of special-purpose hardware, computing equipment, soft- ware, and organizations within the laboratory responsible for the design, maintenance, and use of the system. A. Functional Description Before attempting to delineate the parts of the system, an overview of the functional elements and requirements will serve as a basis upon which to build the description of the system. Figure 1 shows the functional elements and their relationships. General command requirements and sequences are created by a Mission Planning Team (Box 1). This information, combined with the present state of the spacecraft, is used to generate the command strategy, that is, the exact sequence of commands required to change the present state of the spacecraft into that required for the mission plan (Box 2). In real time, the hardware of the Multmission Command System is configured (Box 3) to support a specific mission. The configuration and subse- quent .performance are monitored (Box 7) to insure usability. Also in real time, the commands generated in Box 2, above, are translated into sequences of bits (digital patterns) (Box 4), which are used to modulate the ground station transmitter (Box 6). On board the spacecraft, received commands are checked for transmission errors, decoded, executed, and the new state of the spacecraft is telemetered back to the ground (Boxes 8 and 9). Telemetry data and ground system monitor information are used to insure that the commands have been transmitted. and received correctly (Box 5). The telemetry is also used in non-real time as an input to the next command sequence generation (Boxes 1 and 2). Emer- gency, nonstandard, and rapid response to new conditions require complex checking, feedback, and feedthrough paths within the command system. These complex paths, however, do not change the fundamental functions presented above. B. Organizational Structure The organizational structure of the present system is presented in Tables 1 and 2. Table 1 expands upon the functional requirements showing the relationship between the users, designers, and operators of the equipment. The first column provides a reference to the functional diagram of Fig. 1. The second lists the organization that is the primary user of that functional element. The next two columns describe the special-purpose hardware required for the function and organization responsible for its design. Similarly, the general-purpose computing equipment, the software for it, and the design organization are listed. in the next three columns.. The last column lists the organization responsible for operating the equipment. Table 2 uses the information of Table 1 rearranged in terms of the four major functional installations within the command system. These are presented in the center of the table and are: (1) Mission planning, command generation, and com- mand simulation. (2) Mission computing and control. (3) Deep Space Network and network control. (4) Spacecraft command equipment. Flanking this listing are the organizations responsible for the development and for the operations of each installation. C. Present Implementation and Capabilitiess The following discusses, in general terms, the equip- ment used by the present command system to meet the functional requirements. It is organized along the equipment boundaries rather than the previumly de- scribed functional boundaries. 1. Ground communications. The communications of all command-related information between the control instal- lation (Mission Control and Computing Center (MCCC)) ,A and the Deep Space Station (DS5) is over the high-speed. data line (HSDL). The data are sent serially in blocks of 1200 bits at a rate of 4800 bits/s. Block throughput rate for this duplex channel is 99.5% (Ref. 1). This HSDL bit rate, however, does not adequately describe the transfer rate of commands through the high-speed data line. When the block structure is examined in detail (Refs. 2 and 3), it is seen that the maximum command word rate, for commands of 71 bits or less, is about 1 per second. For present bit rates this is more than adequate. However, for command element radiation times approaching 1 com- mand element per 2 seconds, serious dif ficulties may be encountered. The overall channel is protected against errors within the block. The probability of accepting a bad block .is less than 2 X 10"10. This is provided by a 33-bit polynomial check word sent as part of each block. Line outages are defined as a minimum of 10 blocks in error (Ref. 4). These outages are protected against. by a feedback path between the DSS and MCCC. The mean-time-to-failure of this type of outage has been measured at 4.76 hours. In addition, 87.5% of the outages have a duration of less than or equal to 1 minute (Ref. 4). Therefore, the probability of an interruption exceeding 1 minute is 6.25 X 1". The CMA can operate at rates up to 1000 bitsi s to a resolution of 1% or less (10 µs in period). The resolution in setting other frequencies associated with modulation is 0.1 Hz from 1000 Hz to 1 MHz. The measured reliability and repairability figures taken from continuing performance studies are: .mean time between failures (MTBF) - 196 hours, mean time to repair (MTTR) = 14.5 minutes. These figures include the reliability of both the TCP and CMA (Ref. 7). A further constraint associated with the CMA is that the bet rate does not exceed 1/20 of the subcarrier frequency. This constraint is imposed by the subcarrier frequency validation circuitry (Ref. 8). 3. Telemetry and Command Processor. The function of the Telemetry and Command Processor (TCP) for command is to accept command bit patterns through the HSDL, check and reject data corrupted by transmission errors, set and check the operation of the CMA, send command words to the CMA at the proper time, notify MCCC of the radiation or abort of each command element, and maintain, under control of MCCC, a stack of commands identical to those contained in the command queue at MCCC. If the HSDL should fail, commands can be entered into the TCP manually. 2. Command Modulator Assembly. The Command Modulator Assembly (CMA) is a special peripheral for the Telemetry and Command Processor (TCP) (Ref. 5). The CMA provides the interface between the TCP and the exciter through which command bits are sent. In addition, the CMA sets and checks the operation of itself, reporting to the TCP both correct and incorrect operations. Because of the multimission requirements, the CMA has bees designed to modulate the exciter with an .FSK or PSK waveform (Ref. 6). Each of these options is controllr d from the TCP. The selection is communicated from mission operations via the Network Operations Control Center (NOCC) over the HSDL. Each command bit is verified both when received by the CMA and when sent to the. exciter. If a. descrepancy should occur at any time during radiation (bit value, frequer^ q w?, dulation index, exciter/transmitter opera- tion, v, , o- JMA or the TCP will cause commanding to abort. =. t!, process, invalid commands are not allowed to reach tkt: spacecraft decoder. The abort condition is also reported to the other elements of the command system so that corrective action may be taken. In addition to the automatic abort actions, a manual abort may be performed. This permits aborting valid but incorrect commands. With the TCP processing command data only., bit rates as high as 32 bits/s have been successfully demonstrated. When processing telemetry, the maximum bit rate is limited to about 8 bits/s. The reliability information given above for the CMA applies to the TCP as well. (MTBF = 196 hours; MTTR = 14.5 minutes.) 4. Command Detector Unit. The following describes a digital Command Detector Unit (CDU) of the Viking type (Ref. 9). This type of device has been accepted by the MJS'77 Project and will probably be accepted . by the MjU'79 Project. The digital CDU acquires both :subcarrier phase and bit .synchronization by maximum likelihood detection of digital correlations performed on the input signal. The phase tracking of the signal is also accom- plished digitally. As presently designed, the CDU demodulates a signal whose subcarrier is fixed at 512 Hz and whose bit rate is selectable at the time of CDU manufacture at 1 Hz or from 2 to 256 Hz in even increments. A bit error rate of 1 X 10-5 is selected as a threshold value. At this.threshold.the probability of false acquisition is 1 X 10 4, while the probability of false out-of-lock is 1 X 10-5. For a single command of the Viking type, the I 96 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 iprobability of incorrect execution is 10- 13 and the probability of failure to respond is 10-3. For a Viking block of 50 words the probabilities are 5 X 10`5 and 5 X 10-2, respectively (Ref. 10). 5. Central Computer and Sequencer Subsystem. The spacecraft Central Computer and Sequencer Subsystem (CC&S) performs several activities in the command chain. The detected bits of a command message are received serially from the CDU, tested for start of message, and assembled into words. The words are decoded, checked for parity, and routed to the appropriate spacecraft subsys- tem. A delay of 10 bit times permits the aborting of a command after it has been received and decoded The abort is indicated by a loss-of-lock in. the CDU. The speed of the present CC&S, with its flight software, permits a decoding bit rate of 50 Hz maximum (i.e., provided the CC&S does no other processing) and a typical decoding rate of 20 Hz. A change in the flight software philosophy could double this rate (Ref. 11). 6. Mission Control. and Computing Center. The Multimission Real-Time Command System accepts the command data as a file and communicates these data to the appropriate DSS. Responses from the DSS are used to verify that commands are sent in a proper and timely way. Full control of the command operation is maintained by the command operator. The Mission Control and Comput- ing Center (MCCC) -DSS software maintains a feedback control of the DSS command subsystem via the HSDL. Mission Control and Computing Center facilities are designed to handle nine DSS/TCPs simultaneously. Each DSS is handled through a communicator having a capacity of 3000 queue elements (71 bits). The functions within the MCCC command system can be .processed at rates greater than 1000 hits/s (Ref. 4). The reliability and maintainability of the MCCC command system. have been measured for a period -greater than 1.5 years These measurements show that the present MTBF is 23 hours and the MTTR is 9 minutes (Ref. 12). 7. Other elements. The Flight Data System (FDS), Network Operations and Control_ Center, and the ground telemetry processing do not have a direct impact upon the multiple-rate capabilities of the command system and . will. not be amplified upon in the present report. Table 3 presents a summary of the above information. IV. Multiple-Rate Command System Certain improvements in the performance of the command function can be obtained by permitting the bit rate of commands to be adjustable in flight. Such a system has been investigated foc feasibility and applicability. The proposed Multiple-Rate Command System (MRCS) would permit the radiation and reception of commands at several rates to one spacecraft. The choice of rates would be predetermined, but the selection would be done in real time during the flight. The CDU is the only component in the total command system that prevents the immediate testing and adoption of MRCS. Philosophically, the changes required to make the CDU compatible with MRCS are small. Likewise, the hardware required represents less than a. 1% increase in the cost of the flight equipment. Before outlining the changes required in the CDU, a brief review is presented of the benefits that MRCS would provide. A. Benefits Obtainable With MRCS The benefits obtainable from MRCS accrue from three sources, (1) increased rates over those of end-of-,mission (EOM) limitations, (2) decreased rates under those usable throughout the mission, and (3) the flexibility in selecting rates as a function of resources. 1. Benefits from increases) rates (above normal EOM). Considering the overall performance of the command system, higher rates will increase the probability of completing a command .sequence. This benefit arises from the moderate reliability of the ground command system. .Measurements to date of ground system reliability show an MTBF of about 13 hours (Ref. 11). Using an exponential reliability function (Fig. 2), this represents a probability of completing an 8-hour command sequence of 54.0%, for 4 hours of 73.5%, and for 2 hours of 85.7%. Assuming for the moment that the 4 to 1 range in rates is compatible with the space link performance, that is that the signal-to-noise ratio (SNR) does not drop below the threshold, the probability that a command sequence could be completed in an 8-hour shift is 54% at the 8-hour rate, 92.9% at the 4-hour rate, and 99.06% at the 2-hour rate. The above figures assume an idealized system operation where repairs require negligible time. The figures, however, do serve to place an upper bound upon the .improvement and to indicate the relative improvement resulting from shorter command sequence times. Furthermore, at 1 bit/s, 8 hours of command represents 28,800 bits. For on-board computers with 18-bit words, this would represent a.16W word update. Such an update is typical for a Mariner class spacecraft. ,i JPL DEEP SPACE NETWORK PROGRESS REPORT 42-26 97 MJS'7'r, a typical spacecraft of the next era, contains 3 computers with 4000 words of storage each (Ref 13). Limiting a worst case update to 80% of the available storage and excluding the loading of the back-up computers, the maximum command sequence time at 1 bz/s would be about 48 hours. Continuous operation for 48 hours has only a 2.5% probability of occurring. At a command rate of 4 bits /s, the time would be 12 hours and the corresponding probability of completing the command update without ground system failure . would be 39.8%. Commanding at 8 bits /s would result in a 6-hour sequence, which could be repeated in a 12 -hour pass, yielding an 86 ,3% probability of completion. An altern::te view of the use of the system would be to limit command sequences to those of a length such that the probability of completion exceeds some value. For the following discussion, 80% has been used as the minimum allowable probability of completion. At the MTBF of 13 hours, this yields sequences no greater than 2 .90 hours. Table 4 gives update sizes versus bit rate for this time (80% of 12,0(10 words equals 9600 words). If such a sequence were sent twice, the reliability would be 96% and take 5.8 hours. For three transmissions, the reliability would be 99.2%, and the time would be 8 .7 hours. This, again, neglects repair time, but for the present system 98% of the repairs would be completed in less than 1 hour, thus increasing the overall time required for the double transmission to less than 6 .8 hours and the triple transmission to less than 10 .7 hours. Both are well within a. 12-hour pass. The command' acquisition time is fixed at 90 bit times. Thus for 1, 2, 4, 8, and 16 bits/s this results in 90, 45, 22,5, 11.25, and 5,625 seconds, respectively. The MJS'77 Project has specified a commanding sequence in which the CDU lock is broken after each block of about 1000 bits (Ref. 13). If sue a strategy is adopted, it will increase the overall active command time required (i.e., the time that the system must be up). This . results in a corresponding reduction in probability of eompletion. For any specific mission with values of STqlNo at the spacecraft and commands sent in blocks of N bits, a series of curves could be generated to provide an optimum . ,strategy at each point in the mission. Aside from the above outline of such a process, the generation of such curves is outside the scope of this report, By completing a command sequence with a high probability in less than 8 hours, a second shift would l obviated. The staffing for command costs about $160,000 per year for a shift of 8 hours, 7 days per week (Ref. 14). For long-term missions such as MJU'79 (11 years), this reduction in operations staffing can result in large savings. The number of commands per unit time has increased as missions have become more complex. With continued increasing complexity; longer .missions, and expanding options witt:in a mission, this increase should continue. The increased traffic places a heavy load upon the DSN. By 1977, 16% of the tracking time will be required for command. This figure excludes exteirded missions and, as a result, is probably low. Furthermore, in these initial calculations, no attempt has been made to include the effects of view period. This also may result in a value too low for some periods. The ability to select a bit rate compatible with mission phase from a set with adequate range will aid in keeping the net loading within bounds. 2. Benefits from decreased rates (below normal EOM). The benefit achievable from decreased bit rates comes mostly from the increase in received SNR over the command channel. The most outstanding benefit of this type is in the event of a. spacecraft emergency where eommandability can be increased. Such a condition has been encountered in the design of the Viking 1975 mission (Ref. 15). At superior conjunction with the 26-m, 10-kW subnet and the low-gain antenna 30 deg off axis (a condition possible through loss of attitude sensor lock), the required bit rate to maintain a bit error rate threshold of 1 x 10-5 is less than the fixed 4 . bits/s. MJS'77 will require the 64 -m, 100-kW .station at its 16- bit/s rate to command out of trouble at Saturn encounter and beyond (Ref. 14). With the present design of the MJU'79 mission, at Uranus encounter and during probe insertion, the spacecraft will be commanded to an attitude where further .command must be at 1 bit /s to be reliably accepted. This condition occurs with the 64-m subnet at 100 kW. With the exception of MJU '79, no provision has been made to avoid these difficulties. The lower bit rates of MRCS would improve the commandability in these cases. MJU'79, recognizing the extent of .the .problem, is requiring that at least 2 rates, 1 and 16, be available. 3. Benefits from the flexibility of hit rate. The flexibility in selecting bit 'rate delivrrs .benefit it) tsvo areasc (1) it permits the optimization of the entire command link over the mission in terms of command reliability (a combine- tian of link performance and ground system reliability), JPt DEEP SPACE NETWORK PROGRESS REPOR T 42.25 3 1 ^9 and (2) it permits the allocation of command activity between the two subnets (26 and 64 m). B. Changes Required to Support MRCS In this section only those changes required to test and apply MCRS will be discussed. This set of changes may not result in the most efficient MRCS, but does result in an MRCS with a lower overall system impact. The final section will discuss briefly those areas which require further study and which may result in a more optimum system. 1. Changes required of the ground syste m. No hardware changes are required for the ground command system to be able to support MRCS up to a rate of 16 bits/s. However, procedures must be developed to permit the changing of rate during a pass, monitoring this activity, and verifying it. This requires the coordination of activities between Mission Operations System (MOS) and NOCC. The DSS is transparent to these activities. 2. Changes required of the flight system. The changes required of the flight system are of both the .hardware and software type. Two elements of the command subsystem hardware are affected. First; the CDU rate selection must be made flight programmable. Second, an interface from the CC&S to CDU must be developed to activate the rate change. The change in flight software involves only a small expansion to handle the CDU interface. It does not represent a change in philosophy. This modified on-board command subsystem is shown schematically in Fig. 3. Command modulation delivered from the Radio Fre- quency Subsystem (RFS) is processed by the digital CDU. The demodulated command bits, with indicators showing CDU status, are sent to the CC&S where the commands are decoded. When a rate selection command is recog= nized, the pertinent information is sent back to the Rate Selection Storage Register through an appropriate interface. Data from the Rate Register are communicated in.parallel: with. the CDU where it. controls timing signals. 3. Use of MRCS. The spacecraft command operation can be broken into two subtypes: (1) discrete command- ing, and (2) on-board computer .updating. Discrete commanding is characterized by a .low density of command words; therefore, k,o appreciable gain can be obtained by increasing the bit rate. However, computer updates are characterized by high command density and would benefit from higher bit rates. .A command sequence involving a computer update would probably consist of: (l) acquisition of command uplink at lowest rate, (2) transmit rate change command for higher rate as a discrete command, (3^ break bit sync lock and reacquire higher bit rate, (4) transmit update at high rate, and (5) transmit rate change command for lowest rate. In addition, the CC&S would be required to monitor command activity. If no activity occurred within a given period. of time, the CC&S would command the CDU to the lowest rate. This sequence of operations would insure optimum commandability at all times excluding spacecraft emer- gency, and would provide for greatest commandability in the event of a spacecraft emergency. C. Other Approaches to MRCS and lwir Impact The approach discussed so far has assumed that the CDU resides within a flight. command system which includes the CC&S. While this simplifying assumption is valid for JPL spacecraft, it may not be so industry-wide. Two approaches have been considered for a "stand- alone" CDtJ which would meet the MRCS requirements. The first includes, essentially, a limited decoder which would process a command message header and set its operation for the proper bit rate, . The second approach woul,t determine, without the aid of a special header, the bit rate being transmitted and lock to it Analysis of these two options is still in progress; thus a complete and fair comparison of the two approaches cannot be made at this time. Preliminary studies, however, indicate that the first of the two approaches (i.e., a CDU containing a .limited decoder) would require changes in the M000, DSN, and NOCC hardware and/or software. This would_ be in addition to those procedural changes required of the base system described in Subsection IVA Neither of these changes would be required for the second type of "stand-alone" CDU. V. Conclusions Multiple-.rate commanding is compatible with the major portion of the present command system. It would provide advantages in . system . reliability; network loading, and operations costs. Ground system effective reliability can be increased from 2.5 to 86.3% for a worst-case onboard computer load. By permitting optimum rate commanding through either the 26-m or 64-m subnets; the availability of the total network is increased. The shorter command ' !PL DEEP SPACE NETWORK: PROGRESS REPORT 42-25 99 lI periods will, further, reduce operations costs, a significant. The work in process analyzing the above candidates for effect for the long-term missions of the next era. These performance and total system impact will lead to an advantages can be obtained without extensive and costly optimum on-board cniT. By considering the total system changes to the present spacecraft/ground command impact, such a CDU will he optimized in the global sense system. rather than in the narrow confines of its discipline. References 1. McClure, J. P., 4800 bps High Speed Data Error Statistics, IOM, Jan. 5, 1973 (JPL internal document). 2. Deep Space Network Systems Requirements—Detailed Interface Design, Section IV (Command), 820-13, Apr. 15, 1.972 (JPL. internal document). 3. Poulson, P. L., White, J. H., and Frasier, C. E., Division Software Planning Document for the Redesign and Implementation of the MCCC Command Subsystem, 1824-1, Rev. A, May 15, 1973 (JPL internal document). 4. McClure, J. P., High Speed Data Outage and Block Burst Distribution, IOM 3380-73-175, Nov. 8, 1973 (JPL internal document). 5. Operations and Maintenance, Command Modulator Assembly, TM 01105, Feb. 15, 1971 (JPL internal document). 6. Telecommunications Systems Design Techniques Handbook, Technical Memorandum 33-571, edited by R. E. Edelson, Jet Propulsion Laboratory, Pasadena, California, July 15, 1972. 7. Frampton, R., and Tucker, W., Command System Monthly Report for May I974, IOM 421-PF-CMD021, Jan. 5, 1974 (JPL internal document). 8. Allen, W., Command Standard, IOM 3381-74-113; June 12, 1974 (JPL internal document). 9. Tegnelia, C., and Meahl, M., Final Report, Digital Command Detector Development, 900-547, Apr. 28, 1972 (JPL internal document). 10. Mathison, R. P., "MJS'77/V0'75 PSK Command System," presented at the PPDSWG Meeting, jet Propulsion Laboratory; Pasadena, California, Apr. 22, 1974. 11. Emerson, R. F., Comments on Reliability for Command, IOM 331-74-92; July 24, 1974 (c.f. Emerson, R. F. IOM 331-74-92, Extensions, IOM 331-74-102, Aug. 7, 1974) (JPL internal documents). 12. I:ong, R:; Weekly MCCF Reliability Report, June 30, 1974 (JPL. internal document). I& McKinney, J. C. "MJS Command System Project Requirements Overview," presented at. the End-to-End Command Study Team, Jet Propulsion Laboratory, Pasadena; California, June 26, 1974 . 14. Pierson, R.., Proposed MIS "77 Command Baseline .Design Change, IOM 3621- 73-021 Feb. 5, 1973 (JPL internal document). 15. Byers, R., ."Command System," presented at the PPDSWG .Meeting, Jet Propulsion Laboratory, Pasadena, California, Apr, 22, 1974. 100 JPt. DEEP SPACE NETWORK PROGRESS REPORT 42-25 `— Table 1. Functional delegation to organizations -.b Mp Function Userorganization Special hardware Development organization Computers Software Development organization Operation organization 1. Nfission Project Office (200) None — 360/75 nonreal Sequence of events Flight Applications. Mission Computing M planning Project Engineering time (Mission Programming Section (918) Division ( 290) Computing Section (915) Z Facility (161CF) ) ^. 2. Cenerate Project Office ( 200) None — 1108 nonreal time Assembler for on- Data Systems En- Science and Engi- command Project Engineering ( Scientific Com- board computer gineering Section veering Computing strategy. Division (290) puting Facility command genera- ( 916), (292), Section (914) (SCF)) Lion simulation ( 361), (383), Mission Computing 360/75 real and Sequence generation ( 340) Section (918) ' M nonreal time Command genera- Flight Applicationstion and simulation Programming m Section (915) 7 3. Configure DSN Systems Engi- Network Control DSN Data Systems Mcdcomp NCS Command DSN Data Systems DSN Facility ground system necring ( 43(Y) Systems— Development Sigma 5 [real time] System Development Operations (42,2) ^t Space Flight Opera- Computer Network Section (338) (Network Data NCS Support Section (338) - tions Section (295) (NOCC) Processing Area Program (NDPA) ) 4. Translate Project Office ( 200) None — 360 /75 real time Real-Time Multi- Data Systems En- Mission Computing commands Space Flight Opera- (MCF) mission Command gineering Section Section (918) Lions Section ( 295) S; strm—Command (916) Translator Flight Applications Programming Section (915) 5. Process Project Office ( 200) USN-receiver R.F. Systems De- Interdata 4 (Data. Data Decoder D5i\ Data Systems USN Facility telemetry Project Engineering Subearrier demod- volopment Section Decoder Assembly Program Development Operations (422) ( for e0mulaud) Division ( 290) ulator ( 335) (DDA)) TCP Program Section ( 338) Itission Computing Space Flight Opera- Symbol synehron- DSN Data Systems SDS 920 (TCP) Ideal-Time Multi- DSN. Data Systems Section (918) tions Scotion ( 295) izer Development See- 360/75 real time mission Telemetry Development Data decoder Lion (338) ( MCF) System Section (338) Block decoder Flight Applications Ground communi- Programming cations equipment Section (915) I-ISDL 0. Transmit Space Flight Opera- Transmitter and H.N. Systems De- SDS 910 (Antenna Antenna Pointing DSN Data Systems DSN Facility commands lions Section (295) modulator vclopment Section Pointing Sub- Subsystem Program Development Operations (422) Antenna ( 335) system (APS)) TCP Program Section ( 338) Mission Computing Antenna Control DSN Engineering 'Telemetry and liealTime Multi- Data Systems En- Section (918) Processor Section ( 332) Command Pro- mission Command ginecring Section Command Modu- DSN Data Systems censor (SDS920) System (916) lator Assembly Development .(TCP) Ground'communi- Section (338) 360175 Real-Time cations equipment System (MCF)0 Development organization DSN Systems En- gineering (430:) Spacecraft Com- puter Section (361) Spacecraft Data Storage Section(363) Guidance and Control Division (390) System Design and Integration Section (292) Software- Operation organization Per.y ctv Function Userorganization Special hardware Table 1 (contd) Development organization Computes 7. Monitor ground system.(see No. 3 (NCS) ) 8. Process Project Office .("200) Spacecraft radio Spacecraft Radio On-board control commands Command Section .(336) computer (CC&S) Detector Unit Spacecraft Tele- do-board data Modulation De- communications computer Flight tector Assembly Section ( 339) Data System i, (MDA) (FDS) Guidance and control computer (APS) I I ^ Table 2. Installations versus organizations Development Functional Operating organization installation organization Data Systems Engi- Mission planning Mission Computing neering ( 916) (918) r `. Flight Applications Command Science and Engi- Programming ( 915) generation neering Computing Command. (914) simulation Systems Design and Integration (292) Spacecraft Com- puters ( 361) Spacecraft Data Storage (363) Guidance and Control (MO) Data Systems Engi- Mission computing Mission Computing neering ( 916) and control (918) Flight Applications Programming (915) DSN Data Systems Deep Space Network IDSN Facility Opera- Development ( 338) and network control tions (422) R.F. Systems Devel- opment (335) Spacecraft Radio Spacecraft command Space Flight Opera- (836) equipment tians ( through com- Spacecraft Telecom- mind link) ( 295) munications (839) Spacecraft Com- puters ( 381) Spacecraft Data Storage (303) Guidance and ' Control (340) JPL DEEP SPACE NETWORK PROGRESS REPORT 42 -25 103 . -m'I, 4NN t T' Table 3. Performance characteristics of system elements Reliability Element Throughput Flexibility Error rate Accuracy MTBF MT3'RS Redundancy High-speed data 4800 bits/s 4.79 h for outages 14:8 m Partial or full N/A From l X10-5 to NIA line (HSDL) 4-1200 bit blocks/s; of 10 blocks or a = 0:9958• 5x 154 bit error rate 9 command words/ more From ax 10-4 to block _ 1 command 38 h for outages 5x 10-+ block error word/s (includes of 1:min or more rate feedback checking) 1x2-aq undetected Block throughput bit error rate rate 99.5% Command 1(IDO bits Is 199-h (includes 14.5 in Partial or full: Nwe Theoretical (pre- Modulator TCP) a = 0;9988 (1) Frequency shift dieted) bit error rate Assembly (CMA) keying (FSK) 1 x 10-11 (2) Phase shift keying (PSK) (3) Direct carrier phase modula- tion (4) PSK-PN (sync? (5) PSK- X Manchester 11 coded M Subcarrier 100 Hz 0:1-Hz resolutionV to 1 MHz y Sine or squarewave 10-Ecs resolution in data rate 1 bits to period above hn 1 kbit/s 1 bitsZ Modulation voltage 3.14-mV resolution 50 to 800 mV peak F'SK frequency 0:1-Hz resolutionX 100 Hz to 1 MHz accuracy is tied to station reference frequency H Telemetry and 32 bits/s no 198 h (includes 14.5 m Partial or full Programmed far N/A N/AN Command Proees- telemetry CMA) a = 0:9988 multimission appli= asor (TCP,) 8 bits/s telemetry cation iu P 4— Table 3 (tantd) v v Reliability Element Throughput Flexibility Furor rate Accuracy a MTBF 1,,I T R—S Redundancy Command Detector 256 bits-/s - Full` 1 to 256 'bits/s Bit error rate at N/A Z O: as . A' N Centrul'Computer 50 bits/s command — and`Sequeneer decoding only (CC&S) 20'bits/s shared tasks Doublable with a change inflight . software . Mission Control and >1000 bits/s 24 h Computing Center (MCCC) Flight Data System (FDS) Network Operations Irate change con- and Control; Center finned within 5 (NOCC )" min—manual -( Block 11—Block ill) MTA.F •" uptime ratioMTBF +'MT^?R (even rates) threshold, SNR + 10.5 dB, 1xlW% Acquisition Failure 1 X 10-+. False out- of-lock 1 x to 5% Single command: -- Incorrect execution 1 x 10-6. Failure to respond 1X10-s. 50-word block com- man&. Incorrect execution 5x10-6. Failure to respond 5X 10-2. Full Fully programmable N/A N/A 9 min Partial or full Fully programmable N/A N/A a 0:9932 Full U rfted format N/A N/A selection N./A N/A N/A Table 4. Bit rate versus update size Bit rate, bits/s Approximate wards in 2.90 h 1 580 2 1160 4 2320 s ' r; S 4640 16 9280 32 1$560 64 37120 3 128 74240 3 - -. 106 _ - - - - - !PL DEEP SPACE NETWORK PROGRESS REPORT 42.25 41 .. 6TRANSMIT COMMAND 7 3 .I iI l ' ¢ I d _ i. c CONFIGURE GROUND SYSTEM NOCC F E 3 2 4 MISSION COMMAND TRANSLATE PLANNING STRATEGYCOMMANDS PRO i PRO.! MCCC 5 PROCESS TELEMETRY PROCESS COMMAND S/C 9 TELEMETER COMMAND STATUS S/C Fig: 1. Command System functional block diagram ;T f t 0 LOCK INDICATORS__ - FROM t UITAL COMMAND CCBS RFS BITS ? {_ I RATE SELECTIONRATE SELECTION. COMMAND STORAGEREGISTER AND SERIAL TO . _...._. PARALLEL CONVERTER Golay-Viterbi Decoding: Results of the MVM'73 X-Band Telemetry Experiment L. D. Baumert and R. J. McEliece Communications Systems Research Section The X-band convolutionally coded telemetry data from the Mariner 10 X-band telemetry experiment have been used to evaluate the performance of the Golay_ Viterbi concatenated coding system proposed for lfariner Jupiter/Saturn 1977 (MJS'77). On January 15, 1974, nearly 70 minutes of simulated X-band convolutionally coded telemetry was recorded at the Goldstone 64-m antenna station. One object of this experiment «sts the quantitative evaluation of the K = 7, rate',- convolutionally coded, Viterbily decoded telemetry system which is scheduled for use on all Mariner-class spacecraft after 1976. The relevant experimental parame- ters were: Data rate: 2.9 kbA Nominal Eb/No: 3.0. dB Data sequence: . • . 10101010• Code sequence: •••11010111010111010•. Subcarrier frequency: 177.1 Wfz Symbol Synchronizer Assembly (SSA) matched filter quantization: Sign plus 5 bits magnitude The bit error probability was calculated over intervals of 1-min duration; the results are shown in the upper curve of Fig. 1. Notice that the bit error Probability exceeded the nominal threshold of 5 X 10- during the latter half of the experiment. For further details of this part of the experiment, consult the memo by Springett and Kollar (Ref; 1), After the telemetry was Viterbily decoded, an error tape, containing about 10- bits, 1 denoting an error, 0 no error, was produced. This tape was tlien "decoded" by a Golay decoder identical to that proposed for use in the . MJS'77 concatenated coding scheme for nonvideo teleme- try (clef. 2). That is, the Viterbi error sequence was assumed to be a sequence of noisy 24-fold interleaved 24-bit. Golay eodewords, and each such codeword was decoded according to the decoding algorithm BI of j Ref. 2. Again the bit error probability was calculated over 1-min intervals; the results are shown in the lower curve of :Fig. 1. Notice that the Golay decoder made no bit errors until the Viterbi bit error P, probability exceeded the 5 X J0_, threshold- However, during the periods when P,. > 5 X 10-", the Golay performance also exceeded its threshold 5 X 10-51 208 1 1 E References 1. Springett, J. C., and Kollar, F. J., "Results of the NIVI NI73 X-Band Telemetry Experiment," {private communication, May 1974. 2. Baumert, L. V., and. N-IcEliece, B. J., ."A Gol .ay-Viterbi Concatenated Coding Scheme for NI,I;S 77," in The Deep Space Network, `Technical Report 3`?-1526, Vol. XVIII, pp. 7$-84, Jet Propulsion Laboratory, Pasadena, Calif., Dec. 15, 1973. i a is A INTERLEAVED (24,12) GOLAY-VITER91 DECODER PERFORMANCE AT 1.45 kbps I 1 11. 1.0'3} r+ m a O O M 10. m_ NONVIDEO SCIENCE 5 X 105 REQUIREMENT FOR MJS 177 10 5 0 (K=7, 81112) VITERBI DECODER PERFORMANCE AT 2.9 kbps TIME, min Fig. 1. X-band.telemetry experiment coded data results 1 ^ ^l 1 3 } s ^ }I A Signal Combiner for Antenna Arraying H. Witck Communications Systems Research Section The signal combiner performs the phasing and summing of a high data rate spacecraft telemetry signal received simultaneously at three DSN stations. The signals are combined at the subcarrier level after they have been microwaved to a common site. Before -:-,mming the signals the combiner delays them by the amount necessary to compensate for differences in phase due to unequal station- to-spacecraft distances and microwave delays. A tracking loop continuously adjusts for changes in signal delay so that correct phasing is automatically maintained throughout the spacecraft pass. The signal combiner was successfully used in an experiment designer] to im- prove the quality of real-time video data of the Mariner 10-spacecraft at its second Mercury encounter. Two 26-m antenna stations -were arrayed with one 64-m antenna station at the Goldstone Deep Space Communisations Complex. This _ combination produced an improvement in signal-to-noise ratio of 0.8 dB when compared to the 64-m antenna station by itself. 1. Introduction site. Compensation must be made for all of these delays i if a meaningful combination of the signals is . to . be A spacecraft signal received simultaneously at several achieved, tracking stations is affected by an independent noise con tribution . at each station. An . improvement in signal -to- Signal combination at the radio frequency (RF) or noise ratio (SNR) can therefore be obtained by combining intermediate frequency (IF) level would be most de- the outputs from various receiving locations in an appro- sirable, but the technology for synchronizing the signals priate manner. This technique is sometimes referred to as to the degree required is not yet available. Combining "station. arraying." Due to differences. in space Ft-to- the signals at the subcarrier level, where synchronization. i station distances, the signal arrives with a differe3. play requirements are less severe, is an attractive alternative. a at each station. These delays vary with spacecraft posi- In .fact, if the distance between stations is small and the l tion. Further delays, which are fixed but generally un- ' data rate and subcarrier frequency are low=, such that the equal; are incurred in .relaying the signals to a common .. delay difference amounts to only a small fraction of the .. i JPl DEEP SPACE NETWORK PROGRESS REPORT 42-25 111 i I r bit time, the signals can be combined. without delay with optimum weighting (discussed in a later paragraph compensation. This has been demonstrated by J. M. on "mixing ratio") and perfect phasing, the SNR of the Urech (Ref. 1). At higher data rates and subcarrier fre- sum is . quencies a variable delay device is needed to phase the signals correctly. The design of the signal combiner was SNR„ = SNR, + SNR,. + SNR:, motivated by the problem of phasing the Mariner 10 117.8 kbits/s telemetry signal from three stations to an where accuracy of 85 ns.(10/6 of the bit time), with signal delays varying over a range of more than 50 Its during an 8-br SNR„ = SNR of the combined signal period. The signal combiner provides delay compensa- tion that automatically tracks the changing signal delays SNR, = SN.R of the signal from 'DSS 14 and keeps the signals .correctly phased throughout the spacecraft pass. The combiner also performs the summa- SNR_ =SNR of the signal from DSS 13 tion of the properly p:lased signals. SNR, = SNR of the signal from DSS 12 The improvement in SNR of the combined signal over 11. Mariner 14117,6-kbits/s N Enhancement that of the 64-m antenna station by itself is Experiment Two 26-m antenna stations, DSSs 12 and 13, and one SNR, SNR,_ SNR — + . _. .. .} SNR,^ 64-m antenna station, DSS 14, were arrayed for the SNR, SNR, SNR, SNR, reception of the Mariner 10 high-rate TV data during the = 1 t- 0.1 + 0.1 = 1.2 = 0.8 dBsecond Mercury encounter. The purpose of this experi- ment was to improve the quality of real-time video data The following definitions are useful. for discussing the and to demonstrate the arraying technology, Figure 1 delay relationships: describes the experiment configuration in general terms. The receiver baseband outputs from DSSs 12 and 13 are DV- = the variable spacecraft signal ;lelay seen at E: DSS 13 with respect to DSS 14. DV = 20 µs,microwaved to DSS 14 via GCF 10; the Communications p. Switching Center located at DSS 12. The baseband out- means that the signal arrives at DSS 13.20 µs puts consist of a. 1771 kHz squarewave subcarrier modu- later than at DSS 14) lated. by 117.8-kbits/s telemetry data. The DSS 14 re- . ceiver baseban,: output is microwaved to CCF 10 and DV:, = the variable signal delay seen at DSS 12 with back to rc tlizo a faxed signal delay of 110 µs. This is respect to DSS 14 necessanv, to assure thpt the signal from DSS 14 arrives later at the combiner input than the other two signals, at DF_ = the fixed delay incurred in rnicrowaving the all tiimes. At DSS 14 the three microwaved .baseband signal from DSS 13 to DSS 14 signals are fed to the input of the signal combiner., which delays the signals from DSSs 12 and 13 by the amount DF:, = the fixed delay incurred in rnicrowaving the . required to synchronize them . with the signal from DSS signal from DSS 12 to DSS 14 14. Once properly phased, the signals are affected by a. g weighting factor according to their individual SNRs and DF, = the fixed delay in microwaving the signal combined in a summing amplifier, The weighting factors from DSS 14 to GCF 10 and hack to DSS 14 are chosen to optimize the SNR of the .sum. The com- r Isined signal proceeds from the output of the signal com- DC, the variable delay the signal combiner must biner to the baseband input of the Subcarrier Demodu- impart to the DSS 13 signal in order to phase later Assembly (SDA). From there on, the signal is itwitl3 the DSS 14 signal> ]processed in the normal .manner by the :rest of the: telem- etry chain. DC;, =the variable delay the :signal combiner must impart to the DSS 12 signal to phase it with The three participating stations were in the "listen- the DSS 14 signal. only" mode for the experiment. The baseband signal SNRs of the 28-m antenna stations were about 10 dB The signal combiner does not delay the signal from below that of the 64-m station. Assuming signal addition DSS 14. 112 JPL DEEP SPACE ..NETWORK PROGRESS REPORT: 42-25 l ^ If the three signals are to arrive at the summing point in phase, the total delay incurred by each must be the same. Therefore DF, = DV' + DF•, + DC^ DV, + DF, + DC, so that DC, -- DF, — DF, DV;: DC,, = DF., — DF, — DV, where DF, = 110 µs DF.. = 82 !,s DF;, = 55 pus DVS --57to+6 µs for Mercury H encounter DV_, = 43.to + 9 µs From the above it can be computed that the signal com- biner had to provide delays ranging from 22 to 85 tLs for the DSS 13 signal and 46 to 98 lcs for the DSS. 12. signal; IV. Detailed. Discussion of the Signal Combiner The three combiner input signals are conditioned by three essentially identical input amplifiers provided with front panel adjustable attenuators and rms voltmeters to monitor the amplifier outputs. The signal + noise volt- ages out of all three amplifiers are set to the same level. This makes it easier to obtain known mixing ratios. The .input amplifiers limit the signal bandwidths to 1 MHz to prevent aliasing in the sampling process that follows. From the input amplifier, Signal 1 proceeds directly to the summing amplifier; however, at . the same time a quantized version of the signal is produced by a sample- and-hold (S/H) followed by a 1-bit analog-to-digital (A-D) converter. The sampling rate is 2.5 MHz. This digitized version of Signal 1 is used only for the purpose of correlation with Signals 2 and 3. After passing through its input amplifier, Signal 2 is sampled .at a rate of 2.5 MHz and then quantized by an 8-bit A-D converter. The 2.5-MHz sampling rate was chosen so as not to degrade the 177.1-kHz squarewave subcarrier appreciably. The use of an 8-bit A-D converter makes the quantization error negligibly small. The rate of change of the variable delays was less than The 8-bit . samples then pass through a serial FIFO10 'as/h at all times, i.e., dDV_/dt C 10 µs/h and buffer. The buffer output rate is determined by a fixeddl)V,/dt C.10 tLs/h: 2.5-MHz clock, .while the buffer input rate is governed . by a separate variable clock of approximately 2.5 MHz Ill. Brief Functional description of the Signal but asynchronous with respect to the output clock. Making 3the input clock slightly faster than the output clock willCombiner cause the number of samples stored in the buffer (buffer Figure 2 shows a block diagram of the signal combiner. fill) to increase, since more samples are put into the Signals 1, 2, and 3 are the baseband signals from the buffer than are withdrawn. Conversely, an input clock three receiving stations to be .combined. Signal 1, which lower in frequency than the output clock will cause the i arrives more delayed than the other two, is fed directly buffer fill to decrease. The length of time a sample re= t^ the summing amplifier. Two identical but indepen- mains in the buffer (delay) is a function of buffer fill and dently variable delay channels (Channel A and Channel the phase difference between input and output clock. B ou the diagram) bring Signal 2 and Signal 3 into .phase Therefore. the buffer delay can be continuously adjusted agreement with Signal 1 before they reach the summing bv controlling the input clock frequency. The approxi- 1, amplifier, where the three signals are added to produce mate buffer delay can be calculated using the formula the combined. output. BUFFER DELAY = BUFFER FILL i Briefly, each delay channel functions as follows: The x CLOCK PERIOD signal to be delayed is sampled at a rate of 2.5 MHz: The samples are then converted from analog to digital form The maximum delay that can be achieved obviously and. stored in a first in/first out (FIFO) buffer for a con- depends on the length or capacity .of the buffer. The trollable length of time (delay). The control for the buffers used in the signal combiner are 8 bits wide X buffer delay is derived from the correlation of the buffer 512 words long. With a clock period of 0.4 tcs the delay output with Signal 1.. After leaving . the FIFO buffer the . would be 512 X 0.4 tas _ . 204.8 ps fora completely full delayed samples are reconverted to analog and fed to the buffer and zero for an empty one. In practice, however, summing amplifier; due to internal propagation time limitations the buffer I JPL DEEP SPACE > NETWORK PROGRESS REPORT .4226 113 F WA:..:.,_ i 11^ S cannot be run completely full or completely empty at 25 MHz, so that the actual maximum delay is about 180 Its and the minimum is 20 µs. Parallel and series connected Fairchild 3341 FIFO memories (Ref. 2) were used to implement the delay buffers. A digital front panel display of the buffer fill is provided as an acquisition aid. At the output of the FIFO delay Signal 2 is correlated with Signal 1. This correla- tion, which is maximum when the signals agree in phase, is digitally displayed on the front panel. Furthermore the difference of the correlation of Signal 1 with Signal 2 advanced 90 deg of subcarrier phase and that of Signal 1 with Signal 2 retarded 90 deg is also developed. This difference, designated "quadrature" correlation, crosses zero when Signal 2 agrees in phase with Signal 1 and is, therefore, suitable as a control function for the delay tracking loop. Values for both the correlation and the quadrature correlation are generated once a second, The quadrature correlation passes through a front panel controlled digital attenuator, which provides a means to manually adjust the loop gain, A 16-bit digital - to-analog (D-A) converter translates the digital quadrature correlation values into an analog voltage, which is applied to the input of a voltage- controlled oscillator (VCO). The D-A converter output is also displayed by a front panel voltmeter. The VCO consists of a John Fluke 644A frequency syn- thesizer adjusted so that the input voltage controls its frequency over a range of 20 Hz around a center fre- quency of 2,5 MHz. The VCO can also be switched to manual control, which is required during acquisition. The output frequency of the VCO determines the FIFO buffer input clock rate, thus closing the loop. The control loop functions as follows: It is ass,ir ed that Signal 2 is initially in phase tivith Signal 1. If Signal 2 now advances ( in phase) with respect to Signal 1 the quadrature correlation increases. This causes the VCO input voltage and, therefore, its output frequency to rise, making the FIFO buffer input clock rate higher. As a consequence there is an increase in buffer fill and delay, retarding Signal 2. The action of the loop tends to bring Signal 2 back into phase with Signal: L The phasing error is less than 50 ns. As can be seen in Fig. 2, Signal 3 is prt ces^,ed by Channel A in the same manner as Signal 2 is by Channel A. Signal 2 and Signal 3 are weighted by gains a., and a;,, respectively, before they are summed with Signal 1. These gains are chosen to optimize the SNR of the combined signal. The selection of a: and a;, is discussed in a later paragraph. The summing amplifier itself con- sists of an operational amplifier followed by a 50-t2 cable driver and a front panel adjustable attenuator. An rms voltmeter is provided to monitor the combined output. Figure 3 is a photograph of the signal combiner. V. Control Loop Acquisition Procedure The delay tracking loop acquisition -must be performed manually. The loop is opened by switching the VCO control to manual. Monitoring the FIFO buffer fill and varying the VCO frequency by hand, the operator must adjust the delay to within :t 2.8 As of the value for correct phasing. The loop can then be closed by switch- ing VCO control back to automatic. If the delay is more than 2 .8 Its away from the right value when the loop is closed, false lock will .result. This is due to the periodicity of the subcarrier correlation which allows the loop to lock at intervals of 360 deg of the 171.1-kHz subcarrier. Only one of these points, namely where both the sub- carrier and the data correlate, is correct. It is possible ;to find this point by slowly varying the buffer delay and searching for the highest correlation peak with the aid of the correlation display. However, since this procedure can be somewhat time consuming, a Fortran program was written to predict the FIFO buffer fill as a function of time to an accuracy of -f- 2 counts, which corresponds to a delay of ^- 0 .8 i ts and is better than required. The program computes the variable delays from the station coordinates and antenna pointing angle predicts. It then. combines variable and fixed delays to determine the FIFO buffer fill as a function of time and prints it at user selectable intervals. Armed with the program output; an operator can accomplish the task of acquisition in a few seconds. VI. Best. Mixing Ratio The three inputs to the summing amplifier of Fig. 4 are three versions of the same signal affected b y inde- pendent>noise contributions. 'i At the output of the FIFO buffer, Signal 2, which is S = signal power now correctly; phased . with. Signal. 1,. is reconverted to N = noise power analog by an 8-bit D-A converter and then applied to the input of the summing amplifier. SNR = signal-to-noise ratio 8l 114 3PL DEEP SPACE NETWORK :PROGRESS`REPORT 42.25 ^(N j + a^Na) a, Nzl V 11 1 + an ^a) A( N, + a2N2) as V )N, S, + cx_ 52 which is solved by N, S^ N, 53 «'. S,N2 S, N, Inputs 2 and 3 are weighted by gains a2 and a,,, respec- These are the values of a., and a, that maximize SNR, and tively. The weighting should be such that SNR, is maxi- substituting them into Eq. (1) yields mum. Since the signals correlate and the noise does not SNR.,,,,,bK, = SNR, + SNA, + SNR, S1 + a^ S2 + a, K). SNR, _ ^ It can be shown that similar results hold for n inputs with Nl + a"N + aN3 N, S an = SNR is maximum if S,N„ and aSNR, _ aSNR, _ 0 SNR.,..., = SNR, + SN& + • • • + SNR„ aa. ^ a«s For the Mariner 10 television (TV) enhancement experi- ment a value of 0 .3 was used for and a;, with the signal and combiner input attenuator set such that 0-SNR, a1NR, _ a-SNR, agsNR, aa'- 0112 / a, aa3^- ] 0 and c 0 i3al3 - The above conditions result in the system. of equations: S,+N,=S,+N:=S,+Nj The sensitivity of SNR., to a,, and a:, is low, so that their accuracy is not very critical. VII. Conclusion The signal combiner performed as predicted during the preeneounter tests and the Mercury Ii encounter. The combined signal showed an improvement in ST b/N„ of 0.8 ± 0.1 dB over the DSS 14 signal by itself. No signifi- cant operational difficulties were encountered. The Mariner 10 TV enhancement experiment has clearly demonstrated that antenna arraying is practical and can be used to improve telemetry performance. A combina- tion.of two 64 -m antennas, if they were available within the same complex, could produce a 3-dB improvement in signal-to-noise ratio. References 1. Urech, J. M., "Telemetry Improvement Proposal for the 85-ft Antenna. Net- j work," Space. A fro rams Summar Nm 31-63, Vol. 11 116-12o et Propulsionp g ^l, ,1?1?- ^ ^.. p . . Laboratory, Pasadena, Calif., 2. "The 3341 First In/First Out Serial Alemory," Optimos Manual, pp. 74-79, Fairchild Semiconductor, Mountain View; Calif„ September 1972. JPL DEEP SRACE NETWORK PROGRESS REPORT 42 .25 , 115 - y D5514 DSS 14 o SDA etEMAINING TELEMETRY CHAIN } F JJ i COMBINED SIGNAL r-- L Tr D55 13 ^. ._-__ ^^ SIGNAL.1 RCVR a MICROWAVETERMINAL SIGNAL :2. SIGNAL DSS 13 DSS 13 COMBINERSIGNAL 3 ----^ GCF10 C ; - D5S 12 ° MICROWAVE RCVRRCVR TERMINALDSS 12 JMICROWAVE f I TERMINAL D55 14 j q oBASEBAND SIGNAL 117.6 kbps on 177.1 kHz SUBCARRIER Fig. 1. MVM TV enhancement experiment configuration FCHANNEL A SIGN- i SIGNAL 2 INPUTAMPLIFIER SOH AND FIFODELAY BIT CORRELATOR DIGITAL ATT3 NUA- 16-bitD-A i o i 8-bit A-D TOR . ^. 8-hit VCOD-A a2 SIGNAL 1 - INPUTAMPLIFIER SOH AND SUMMINGAMPLIFIER COMBINED OUTPUT1-bit A-D- Q3 a [CHANNEL B SIGNAL 34t. . I Fig..Z Signal . combiner . biock diagram 5 3 i. . ]18 JPL DEEP .SPACE NETWORK PROGRESS REPORT 42-2S POWER SUPPLIES • • • INPUT VOLTMETERS a • ^, OUTPUT 'T INPUT VOLTMETER AMPLIFIERS DELAY AND t. •^• LOGICNG qk. INPUT '0' Q w o r o QATTENUATORS • -oQQ.Q. OUTPUT ATTENUATOR •O ^ __Q • • "0 Q VCO OFFSET 8 r^ CONTROL CHANNEL A VCO -' CHANNEL B^` VCO v v ' k Fig. 3. Signal combiner SI +N1 I S -, N ^2 2 SUMMING2 2 AMPLIFIER CUT 5 NS S 3 + N3 ^3 3 Fig. 4. Mixing ratio JPL DEEP SPACE NETWORK PROGRESS REPORT 42 . 25 117 i t _ 1 a DSN Research and Technology Support E. B. Jackson and A. L. Price R. F. Systems Development Section The activities of the Development Support Croup in operating and maintaining the Venus Station (DSS 13) and the Microwave Test Facility (MTF) are discussed and summarized and progress noted. Major activities include preparation for a planned "automated station demonstration" and equipment modification and testing required therefor, flux density measurements of the radiation from the Planet Jupiter and various radio sources, commencement of active collection of solar energy data at DSS 13, on-antenna testing and successful implementation of the 400-kW X-band planetary radar system into DSS 14, completion of the on-site system testing and shipment of the DSS 43100- kW transmitter system, continued transmission of clock synchronization timing signals to the overseas 64=m antenna stations, expanded activity in support: of the Pioneer I0 and II science program as Pioneer 11 passed by Jupiter, and continued support of various radio science activities planned in the FY 75 JPL Radio Science Plan. During the two-month period ending December 15, Lion is planned using the Venus Station to perform a 1974, the Development. Support Croup, in its operation of pulsar track under remote control from JPL in . Pasadena. the Venus Station (DSS 13) and. the Microwave Test Facility (MTF), made progress on various projects as In addition to the modifications to the computer and 26- discussed herein, m antenna servo system previously discussed (Ref. 1), the vvaveguide switching. system has also been inte&ced with the SDS-930 computer. The SDS-930 computer now has control of the input .termination for the maser, i.e., either I. In Support Of Section 331 the antenna feedhorn or the ambient temperature waveguide 'load .can be selected as the input termination.Stetson Automation (Pulsars) for the maser. The SDS-930 computer can monitor which As part of the overall DSN Station Automation Project termination is in use, and also monitor the polarization (ATOP (18 "Station Monitor and Control"), . a demonstra= which has been selected by the operator. As a result of .j t' lie JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 m previous testing, the servo system has been further modified to connect the SDS-910B antenna pointing input error signals directly to the rate amplifier, rather than coming in through the integrator. The computer now performs the integration with software. This connection is only effective when the computer is being used as part of this demonstration. Testing of the system being automated consumed 121 hours, while actual observation of pulsars, at 2388 MHz, left-circular polarization (LCP), with the 26-m antenna, was performed for 70-1/4 hours. The pulsars observed are tabulated in Table 1. 11. in Support of Section 333 A. Radio Star Calibration With the receiver tuned to 2278.5 MHz, and the 26-m antenna adjusted to receive right-circular polarization (RCP), received flux density measurements were made of radio sources Cassiopeia A, Cygnus A, and Virgo A during 44-1/4 hours of observation. These measurements are made .in a semi-automated fashion using the noise adding radiometer (NAR) with programmer to control antenna movement and data taking cycles through the medium of an interface with the SDS-810B antenna pointing com- puter: B. Sky Survey With the 28-m antenna fixed in azimuth and progres- sively positioned in elevation, 503 hours of . data were automatically collected during the night and weekend hours when the station is not manned. Completing one cycle of elevation positions at 88.8 deg; a new cycle was started at 80A deg, and by the end of the period observations had been taken through 80.6 deg elevation. Additionally, 24 hours of observation of the pole star, Polaris, were performed. All observations are made at 2295 MHz, with the 28-m antenna adjusted to receive RCP and the NAR collecting and storing the data on magnetic tape. C. Faraday Rotation With the two systems under evaluation performing well, the residue of the earlier installation (.two rotating antenna systems, receivers, and test oscillators) was collected and returned to the Stanford Research Institute. Some difficulty was experienced with the data recording system being triggered by noise, but a modification performed by Bruce Parham of Section 333 solved that problem, and, at the end of the period, the system is working well. D. Solar Energy Instrumentation In support of the project to gather precision data on solar energy impinging on the Goldstone area, the Solar Energy Instrumentation Data Acquisition System has been transferred from DSS 14 to DSS 13 along with the associated sensors. This system consists of a multiplexer, analog-to-digital converter, programmer, various readouts, clock, and digital magnetic tape recorder with a small printer providing a record for operator use. Additionally, for off-line use, there is a digital. tape player and a line printer. As currently configured, the system has eight analog and four digital channels, with a capability of approximately 300 total analog and digital channels for which cards are available. Three sensors (outdoor air temperature, dew point hygrometer, and pyranometer) are currently collecting data. The system is installed in building G-60 with the pyranometer installed on the roof. Additionally, two mirror test tables have been set up in the desert northeast of the Microwave Test Facility (MTF). One table will be periodically cleaned while the other will be left untouched; the mirrors on both tables will have reflectivity measurements made periodically. Ili. In Support of Section 335 A. X-Band Planetary Radar Radio frequency (RF) testing at the 300-kW RF power level was successfully accomplished with the feedcone on the .DSS 14 antenna. Full transmit system testing, under closed-loop phase control, was then performed for a 5-hour period; during which careful radiation survey measurements were made. Later, radiation intensity survey measurements were also taken with the antenna in "worst case" Saturn tracking positions. In neither ease were dangerous levels found at any ground' position. The survey is described in more detail elsewhere in this issue. During the first operational radar tracks starting December 10, 1974, the transmitting system performed well, although some trouble was experienced with the receiver and correlator. Later; a malfunctioning traveling- wave tube was removed and replaced in the . buffer amplifier. Although DSS 14 personnel have been provided with red-lined" documentation suitable for operation and troubleshooting, work is continuing on preparation of documentation suitable for transfer,. along with cleanup of the remaining items of Engineering Change Order (ECO) implementation required. A y i t i 1 B. DSS 43/63 100-kW Transmitter Testing The Philco Ford Corporation (PF'C) installation team has left for Spain to aid in the installation of the DSS 63 100-kW transmitter system, and all equipment has been shipped to them. For both systems, modifications have been made to the dual ignitron deck assembues, and successful checkout accomplished. Also, spare filter reactors and all logic cards have been tested while the focusing magnet assemblies have been modified and tested. Using the "test bed," four rebuilt and modified X-3084 klystrons have been tested. One failed the acceptance test and was returned to the manufacturer (Varian Associates). The other three required on-site retuning by a manufac- turer's engineer prior to acceptance. Using one of the retuned klystrons, a 12-hour "stability" test at the 100-kW power level was performed on the RF cabinet destined for DSS 43. After successful. completion of this test, the system was dismantled, the transformer rectifier assembly was weighed (14,5213 kg (32,025 lb)), and shipment to Australia was accomplished. Only minor items remain to be shipped. C. Microwave Power Transmission In preparation for the forthcoming prototype panel testing (March 1975), the power distribution transformer in the collimation tower building was relocated, and ground fault interrupters were put into the circuits to protect all .power outlets. In preparation for installation of the final array, all existing microwave dishes were removed from the tower to minimize wind loading. D. Block 1V Receiver/Exciter (DSS 14) Support of work on the Block IV Receiver/Exciter Subsystem has continued. This work 'included the modifi- cation of the temporary receiver and exciter manual control panels, fabrication of temporary cabling, and general subsystem troubleshooting and maintenance. Subsystem performance .testing and test procedure verification have been started and will continue. In preparation for doppler frequency error tests, the long-run hardline coaxial cables used in the Block IV Receiver/ Exciter at DSS 14: are being tested using conventional procedures, insertion loss, time domain reflectometry and spectrum analysis. Past experience has shown that these tests may locate only the more severe cabling faults. It is therefore planned to use the special Digital Instrumenta- tion Subsystem (DIS) monitor program for final evaluation. 120 If possible, a comparison with similar tests on the present Block III Receiver/ Exciter cabling will be made. Preliminary work has been started to provide the capability for rework and testing of Block IV Receiver/ Exciter electronic modules at DSS 13 utilizing contractor personnel. This would facilitate the completion of the subsystem. A total of 97 manhours of support has been provided at DSS 14 by Development Support Group JPL personnel during the last two months. IV. In Support of Section 391 Differential VLBI As part of the overall DSN effort to develop the capability to navigate a spacecraft using distant radio sources as references, we provided tracking support . to fast-switching VLBI measurements between the Pioneer spacecraft and various reference radio sources. A total of 21 hours of station support, of which 13 hours were actual tracking, was provided. V. In Support of Section 422 Clock Synchronization Transmissions The punched paper tapes, which are used as input data by the station computers with which to accomplish clock synchronization transmissions, have shown gradually increasing error rates due to improper sprocket hole punching and spacing. During the last two months several reschedulings were required and some transmissions were canceled for this reason. When the December tapes arrived, the error rate was so high that complete replacement was necessary. The replacement tapes, which were punched on a different machine at JPL, are usable. During this period six transmissions for a total time of 6-3/ 4 hours have been .made as scheduled by the DSN. VI. In Support of Section 825 A. Pioneer 10, 11 Science Support DSS 13 continued to provide an average of 14.5 hours per week of observation. Measurements of the radiation level from Jupiter and the radio source calibrators tabulated in Table 2 were made at 2295 MHz; with the 28-m antenna adjusted to receive RCP. Observations were JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 kL._.! . 1 4 made for a total of 130-3/4 hours, with the data being tracking, observations were made of the region around semi-automatically collected by the NAR. W51 and S140, using a frequency of 2273.9 MHz with the antenna adjusted to receive RCP. B. Interstellar Molecular Recombination Line Search Similar observations are also made on the DSS 14 64-m Continuing with the attempt (Ref. 2) to detect antenna and are part of the JPL Radio Science Plan for FY recombination lines of carbon, 51 hours of support were 75 described as "Interstellar Microwave Spectroscopy," given to this project. During the 36-3/4 hours of actual OSS-188. References 1. Jackson, E. B., and Price, A. L., "DSN Research and Technology Support," in The Deep Space Network Progress Report 42-24; p. 78, Jet Propulsion Laboratory, Pasadena, Calif:., Dec. 15, 1974. 2. Jackson, E. B., "DSN Research and Technology Support," in The Deep Space Network Progress Report 42-22, p. 111, Jet Propulsion Laboratory, Pasadena, Calif., Aug. 15, 1974. 3C1.7 3C147 3C353 3G18 3C309,1 PKS 0237-23 3C123 3C348 122 Y'. L I I Table 1. Pulsars selected for test observation at DSS 13 (10/16-12/15) 0031-07 1237+25 1929+10 0329+54 1604-00 1933+16 0355+54 1642-03 2021+51 0525+21 1706-16 2045-16 0823+26 1749 -28 2111+46 0833--45 1 fi_8 -04 2218+47 1133+16 1911 -04 Table 2. Radio source calibrators used for Pioneer science support (10/16-12/15) Hybrid Integrated Circuit Development C. F. Foster R. F. Systems Development Section This report describes the development of a single hybrid circuit to replace the control portion of a. I5-line computer interface consisting of 25 discrete integrated circuits. The primary requirements of this hybrid development are the standardization of a logical design to implement the requirements of the Deep Space Network standard interface requirement and the reduction of system downtime due to complex troubleshooting. Introduction The control portion (handshaker) of the standard DSN 15-line interface (Ref. 1) performs all the information transfer protocol and generally relates necessary communi- cation between computer and device before data can be successfully transferred: A handshaker circuit that satisfies these computer and device interface requirements has been designed (Fig. 1) and will function between any desired combination computer and peripheral device. This. circuit is both device and computer independent and operates in the half duplex mode using a fully interlocked request and acknowledge control transfer (Ref. 2). The handshaker circuit contains 25 transistor-transistor logic (1TL) integrated circuit (1C) packages. and 25 wirewrap 1C sockets (Fig. 2) all mounted on a 120 mm x 115 mm circuit board. This method requires 750 connections, 50 of which are for B+ and ground. Because this circuit is designed such that it feeds signals from one stage to another, dependent on conditions within its feedback and/or external inputs, it is-extremely difficult to JPL DEEP SPACE NETWORK PROGRESS REPORT 42.25 is troubleshoot (i.e., even if every IC was replaced with fully tested units, it would take a minimum of 15 min, and the fault could still be in the sockets or in one of the 750 connections). A requirement to reduce Deep Space Station downtime resulted in the investigation of hybrid circuits as a means to replace multiple discrete integrated circuits with -a single package and to provide a standardization of the logic design. 11. Implementation The initial hybrid development utilizes the same TTL circuit design as the discrete design. The TI'L circuit chips are bonded to a package that is 36 mm x 36 mm, with 24 pins. The TTL interconnect circuitry within the hybrid is similar to a standard printed circuit (PC) board in that the circuit traces are etched. Due to its small size, circuit crossovers can be made with short gold wire jumpers bonded to the traces. This ..method, because . it 123 E j a f eliminates the need for multilayer boards to solve circuit crossovers, greatly reduces design time and cost over the conventional PC board. The completed hybrid circuit package is shown in Fig. 3, and a single chip has been enlarged in Fig. 4 to show the wire bonding. III. Conclusion The hybrid handshaker circuit has been successfully evaluated with the coherent reference generator and the PUP-11 minicomputer using the 15-line interface. The hybrid circuit has reduced the system parts inventory by 10 to L. based on stocking one each of every type of IC. The system assembly has been reduced from 750 connections to 48, thereby .improving both reliability and enhancing quality control. By reducing parts by 24 and interconnections by over 700, the system testability has been improved as well as downtime due to testing and repair. Because the TTL, chips can be removed with .beat, the hybrid can be returned to the factory for repair at a fraction of replacement cost. The completed prototype hybrid handshaker will undergo further testing outside of the development group. The results of these tests will be used to evaluate this approach and determine if further design effort is required. References 1. Fry, W. C., Deep Space Network Standard Interface, Spec. ES50834A, June 4, 1973 (JPL internal document). 2. Foster, C. F., Complete Logical Operation and Test Procedure of Handshaker Circuit, Spec. TP510942A, in preparation (JPL internal document). i 3 8 DRDY 9 F1 5 RDY CR6 1 FAIL 'K MING XITOR :K 18 2 SSC 6 DSTD END COUNT RESET 17 3 B—PP b DRSP 15 l 7®F1] 13 2 11 10 Ffl Fig. f. CRG computer interface handshaker logic diagram JiPL DEEP SPACE NETWORK PROGRESS REPORT 42.25 ORIGINAL PAGE 10 OF POOR QUAI - . b Fig. 2. 126 0a i 0 7) 0 0 0 o I Ems. AL, 4 _ 10 Q :ate;I toerr {i J' Fig, 3. CRG computer interface handshaker logic (hybrid) 0RIC,% NL WAGE "I ,V ?00R QL JPL DEEP SPACE NETWORK PROGRESS REPORT 4225 127 aIF -All MIL } ^. t f 1 mm Fig, 4. Hybrid circuit chip mount 128 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 i I Automated pulsar Data Collector S. S. Brokl Communications Systems Research Section The pulsar data collector is a self-contained automated subsystem for the DSS 13 Automation Demonstration. It relieves the 900-series computer from much of the software previously used for data collection. The pulsar data collector is a high speed, periodic signal sampler and integrator which has demonstrated faster operation and higher resolution than existing; devices. Introduction .The automated pulsar receiver (Ref. 1) in conjunction with the pulsar data collector are fully programmable sub- systems for the Pulsar Automation System at DSS 13. The pulsar receiver is a self-contained, 30 MHz- to-baseband receiver with three selectable predetection bandwidths, a diode power detector, an attenuator, and a variable postdetection filter. ..The .pulsar data collector is a self-contained, periodic signal sampler and integrator, interfaced with an XDS 900-series computer. The data collector uses a high speed (4 Its conversion time) 12--bit analog-to-digital (A-D) con- verter. Once the pulsar parameters are programmed into the receiver and the data collector, the computer is free to carry on other tasks as the data collector takes the data and stores them in its own memory. Upon completion, the data collector signals the .computer that the observation has ended. ,allocated to data storage exhaust present memory spa,,e in existing 900-series computers. AIso, with the current pulsar observing system, it is not possible to increase the resolution of the observations while maintaining pl,, ise. The new pulsar data collector is self-contained with its own memory, high speed transistor-transistor logic (TTL), and Schottky logic control elements. It can maintain phase when parameters are changed to expand the reso- lution of the observation. It has no operator controls and can be programmed by any 900-series computer. III. Hardware Implementation Figure 1 is a block diagram of the new pulsar data collector presently installed at DSS 13 and controlled by the XDS 930 computer. The data collector may be used with any 900-series computer without any hardware modifications. The station 1—s tick (1 pulse/s) and a frequency synthesizer are used to establish the precise timing for the data collector. 11. The Problem Limits of the present pulsar timer (Ref, 2) and its im- plementation as a data collector are its low speed and resolution, its heavv reliance on software and its need for large amounts of computer memory space. With DSS 13 automation, large observation programs and memory 3PL DEEP SPACE NM WORK PROGRESS REPORT 42-25 There are two single-instruction Energize Output M (EOM) codes used to program the pulsar data collector from the 930 computer. Both EOM codes are manually set with dual-in-line switches within the data collector. This allows changing of. the instruction codes easily and makes the data collector compatible with any 900-scries computer. 129 E r i 1 The major cycle length is generally set to the period or repetition rate of the observed pulsar. The minor cycle pulses are then the number of samples during this period. The X and Y counters are not stopped between observa- tions, and their reference values are changed only at the eery beginning of a major cycle. New values from the computer are kept in buffer registers. As long as the product of X and Y is kept the same, phase will be maintained between observations. A 16-hit up/dawn counter is used as the N counter with the major cycle pulses-being counted. During observa- tion, the N counter counts down from the number loaded into the N hold. register. When the count reaches zero, a computer interrupt is fired to signal completion of the observation and the counter starts counting up. At the beginning of the next observation, the number counted up to in the N counter is transferred to the D hold register. With each new start command the N counter is reset to a down counter with the value of the N hold register in it. 24 The A and L counter is cleared in the major cycle pulse L 24 and counts up with each minor cy.ie pulse; the maximum count is 2 This counter, in conjunction with two 24-bit N 16 comparators and the s and the L hold registers, controls D 16 the start and end of data collection and the storage of thedata in memory. The value of 3 determines at which. A 13 ±nnor cycle pulse (relative to the beginning of the major iv[ 24 cycle) data are first taken and stored in the first memory location. It can be 0 to 2 2'. The value of L should be the The data stored in the X and Y buffer-hold registers must value of . plus the number of samples to be stared in be the 2's complement of the actual number used as the memory. Data are taken at each minor cycle pulse be divisor for determining minor and , major cycle pulses tween , and L. The value of the number of samples may from the frequency synthesizer input The J register be from I to 800, which is the minimum and maximum stores the delay of the number of minor cycle pulses to size of the memory. One EOM is used for control. When it is followed by the proper Parallel Output (POT) word from the com- puter, it sets up the register pointer or starts the data collector in one of three modes: initial-start, start-on-next- major-cycle-clearing-memory, and start-on-next-major- evele-not-clearing-memory, Initial-start starts the data collector on the next 1—s tick (I pulse/s). The second EOM is used for data transfer. The follow- ing POT or Parallel Input (PIN) word causes the transfer of a 24-bit word from the computer to the register pointed to in the data collector, or from the data collector register to the computer, respectively. The register pointer operates in four modes and sets up the condition for transfer of data between the com- puter and the registers. The memory address counter (A) and the memory (M) are considered registers. In the first made, the register pointer will point only to the register designated in the POT word following the control EOM and will not change until commanded by a new control EOM POT sequence. In the .second mode, the register pointer will increment to the next register in sequence after a data transfer POT has occurred. It will not incre- ment beyond the M position. In the M position, the increment after POT or PIN will refer to the memory address counter (A). The third mode is the same as the second except the increment will occur after a data transfer PIN. In the fourth mode, the increment will occur after a data transfer POT or PIN and is used for memory testing. There are. eight binary registers in the data collector. The maximum number of bits for each register is as follows: X 16 Y . 24 wait after a major cycle pulse before starting data collec- tion. The L register holds the number of minor cycle pulses delayed plus the number of minor cycle pulses to. be used as data points. The N register holds the number of major cycles to be observed. The D hold register cannot he programmed directly but is cleared by every initial start command. The D register holds the cumber of major cycle pulses that have occurred between the end of one observation and the start of the next observa- tion. The X and Y counters are used as modulo n dividers where n max for X = 21c and n max for Y = 2-'. The X counter sets the number of frequenf:y synthesizer pulses for each minor cycle pulse; the Y counter sets the number of minor cycle pulses for each major cycle pulse. 130 JPt. DEEP SPACE NETWORK PROGRESS REPORT 42-25 JPL DEEP SPACE NETWORK PROGRESS REPORT k Pulsars only emit significant radiation during about 1/10 of the period. By using nevi values in the X, Y, A and L hold registers determined from gull-period observa- tions, one can take all the observations during a limited fraction of the period, thus increasing the resolution without destroying the phase of the observed data. The memory address counter is controlled by the start and end pulses froin a and L comparators while data are being collected. Wilen the memory is being controlled 'icy the computer, the address counter is set to an effective memory location when the register pointer is pointing to the A register. The address counter automatically incre- ments at the end of a POT or PIN when the register pointer is pointing to the M register. During data collec- tion, the address counter always starts at zero and stops at L. The memory automatically cycles through starting at zero with each new major cycle pulse. The 8K X 24-bit memory is comprised of two Standard Memories, Inc. SK X 18-bit stand alone memory modules. Every third bit in each module is not used, giving 48,000 spare bits in each module. The output of the memory (M„) R in 2's complement. During the first scan of data after an initial—start or stet-on-the-next-major-cycle-with-clear-memory, the First-N-Inhibit prevents the old data within the. memory from being added to the new data. This effectively clears the memory by storing only the new data in each memory location. During subsequent scans, the contents of the effective memory location are called up, added to the new data point; stored in the adder-hold-register and written back in the effective memory location for each minor cycle pulse. The A-D converter is a Datel ADC-N-12C 12-bit, 2's complement bipolar converter, with a sample and hold module ahead of it. The maximum conversion rate is 4 ps. The data collector is independent of the converter and may be used with new higher speed devices as they become available. The PIN data multiplexer (MUX) allows data from any of the registers or memory to be selectively read into the 930 computer. The register being read is dependent on the register pointer position after a control EOM, as described earlier. IV. Software Table 1 shows the EOM codes and POT bit positions for control of the Automated Pulsar Receiver. Also in-. eluded is a skip-if-signal-not-set (SKS) test for automatic mode. N11hen the receiver is in the local mode the com- puter has no control of the functions. Table 2 shows the EON4 codes and POT bit positions for control and data transfer of the pulsar data collector. An interrupt to the 930 computer is also supplied to signal completion of an observation. V. Conclusion The automated pulsar receiver and data collector are subsystems for the DSS 13 automation demonstration. These subsystems have been installed, tested, and are now operational. The first test results for PSR 0329-54 and PSI1 0833-45 shown in . Fig. 2 give an example of the high resolution available with the pulsar data collector. The horizontal axis is time and is 5,000 samples long. The vertical axis is the power density of the pulsar proportional to the integration number and average received power. Pulsar 0329 has an average rate with a period of 700 ms. Plot 1 shows the results of two, full-period integrations. PIot 2 shows the results of taking the same number of observa- tions during the first half of the period only. Pulsar 0833 has a fast rate with a period of 83 ms. Plot 3 shows a full period observation after an initial start. PIot 4 is. an example of applying the expansion technique, showing greater detail of the pulsar emission. Data points were taken every 8.3 ,as. , 3 I f I I ^ I References 1. roster, C. r., "Automated Pulsar Receiver; in The Deep Space Network Progress Report 42-20, pp. 135-135, Jet Propulsion Laboratory, Pasadena, Calif., Apr. 15,1974. Function SKS 31015 — Skip if receiver in remote EOM 30515 — Reset and disable remote outputs EOM 31115 - Set and enable remote outputs EOM 30115 POT aAttenuator set i EOM 30315 POT Predeteetion bandwidth set i ,i EOM 30415 POT Postdetection bandwidth set ai POT Nord Format Attenuator Six bits, right justified. Minimum attenuation = 01 octal, maximum attenuation 77 octal, 0.5 dB steps from 0 to 31.5 dB. Octal Predeteetion Bandwidth Two bits, right justified. 0 = 10 MHz bandwidth I = Wide bandwidth 2 = 1 MHz bandwidth Postdetection Bandwidth Fifteen bits, right justified. Minimum time constant = 00001 octal, maximum time constant = 77777 octal, Ices steps from 0 to 31 ms. j r I JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 133 FTable 2. Automated pulser data collector control codes Followed Instruction Codea by Function instruction EOM 30016 POT Control, sets up register point and command instructions. EOM 30116. POT Data transfer, from computer to data collector register indicated in control word. POM 30116 PIN Data transfer, from data collector register indicated in control word to the computer. i Control POT Word Format Octal number Function of X register point 02 Y register point . 03 A register point 04 i_ register point 05 N register point 06 D register point 07 A register point 00 M register point lob Increment after POT 20s Increment after PIN 040 Initial start 100 Start on. next major cycle pulse clearing memory 300 Start on next major cycle pulse not clearing memory Data Transfer Word Format Register Maximum ward length X 16 bits, right justified j Y 24 bits .. 24 bits . L 24 bits N 16 bits, right justified D 16 bits, right justified A 13 bits, right justified M 24 bits -Maybe changed by dual-in-line switches in data collector. "May be mixed wit.! preceding control words. 134 JPL DEEP SPACE NETWORK PROGRESS REPORT' 42-2E b r d 9005ER1E5 POT INTERFACE POT BUSS ^ r-- -a X X BUFFER HOLD REGISTER YY BUFFER HOLD REGISTER h CONTROL TRANSFER POT Xo Yo rn EOM I DECODER BUFFER Z X HOLD REGISTER Y HOLD REGISTER X X Y L X COUNTER Y COUNTER 0 REGISTER LPOINTER N m FREQUENCYto - - D A. SYNTHESIZERINPUT _ START INHIBIT N N HOLD REGISTER -V) rn STOP CONTROL FIRST N N° m M 1 FULSE/s TO C) N COUNTER COMPUTERMINOR CYCLE PULSES INTERRUPT N D. DELAY HOLD REGISTERMAJOR CYCLE PULSES U A AND L COUNTER INHIBIT TO MUX D° FIRST N A COMPARATOR L COMPARATOR A ° START END DATA FIRST N INHIBIT Q° Lo A-D CONTROLPOT BUSS 24-bit M0 A A HOLD L L HOLD A MEMORY ADDRESS B K MEMORY 12 bits COUNTER 24-bit ADDER A-D CONVERSION INPUT POT BUSS INCREMENT ADDER POT BUSS FROMCOUNTER RESULT PULSAR M CLOCK ADDER HOLD REGISTER RECEIVER DATA END DEAD DATA MEMORY WRITESTART CONTROLLER CONTROL A-D CLOCK Mo Xo Yo Ao Lo No Do An Y PIN MUX OUT E900 SERIES PIN INTERFACE 2 1 19:05:54 1w MATen WITU CTADT r M N1 KAA !nD rvrl c r, aAa,,.ir- AA Ck—bo Y = 10,000 L = 5000 N = 500 18:24:24 AND 19:32:44 INITIATED AT 1824:24 WITH INITIAL START CONTINUED AT 18:32:44 WITH START X = 200 A = 0 ON NEXT MAJOR CYCLE. PULSE NO CLEAR. TOTAL OF 1000 PERIODS OF DATA Y = 5000 L = 5000 N = 500 Fig. 2. Pulsar data plots, July 26, 1974 I. 3 3 4 19:36:15 INITIATED WITH START NEXT MAJOR CYCLE CLEARING MEMORY x = 100 0 = 5000 Y = 10,000 L = 10,000 N = 500 3 0833 INITIATED WITH INITIAL START X=200 A=0 Y = 5000 L = 5000 N = 500 Automatic Total Recall Program for Replay of DSN 7-Track DOM F. M. Hlavaty DSN Data Systems Development Section The requirement exists for the capability to obtain as complete and accurate a record as possible of all high-speed data communication between the mission control center and the DSN ground stations in support of deep space mission operations. The Automatic Total Recall System was designed and developed for that express purpose. This article describes the functional aspects of the software operating in that system. I. Introduction The Deep Space Station (DSS) Telemetry and Com- mand Subsystem (TCT)) supports deep space mission operations by providing a data detection and processing capability, which in operation with the Ground Communi- cations Facility (GCF) provides a communications link between the spacecraft and the mission control center. The TCD is responsible for transmitting commands to the spacecraft and for recovering incoming telemetry from the spacecraft. In performing mission support functions, the TCD generates a real-time log of all telemetry and command data transmitted over the high-speed data communication link between the DSS and the mission control center. The recording is on a 7-track magnetic tape directly connected to the Telemetry and Command Processor (TCP). The digital tape serves as the Telemetry and Command Digital Original Data Record (DODR) for the TCD. II. Purpose The purpose of the Automatic Total Recall System (ATRS) program is to provide automatic or manual capability for replaying to the mission control center the Digital Original Data Record (DODR) located at the DSS. The objective of the ATRS program is . to create a complete master data record of spacecraft data, as free from error as possible. The need for replaying the DUDR ariser. from the possible prest-iice of &.h outages 5 deg 0.005 deg 5 > EL > 0 deg a ,~ 0.015 deg 0 > EL > --3 deg I. Introduction Ft — (T, f _ JA-,Z) ^1 In a. previous article (Ref. 1) the authors presented a T 1 1 T o '(Z) J new angular tropospheric refraction model which very o,(P,Z) _ (P --- P,,)(exp EA,(Z A2)1) accurately modeled existing .optical angular refraction. data, as follows: T,Z) = (T --- To) feXp [B,(Z — B:)1) r K},3 [U(Z)]' Q3(Z) — (Z — C,) (exp [C,(Z _ C,)]) R=FF 4 eh ^K n : , p 1 + o,(Z) where Pp P — a ^ (P^Z) R refraction, sec Po 1 TA, (Z}}} Z = actual zenith angle,. deg 142 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 EL = elevation angle II, past Attempts to Transform Angular DL 90 deg — Z Refraction Models From Optical to Radio Frequencies ^ —K, ^ U(Z) ^ZK_ To facilitate a discussion of past attempts to generate angular tropospheric refraction models for use at radio K, = 46.625 frequencies, let the following notation be introduced: K, = 45,375 Rop = R(P,T,Z) = optical refraction model from K, = 4.1572 above K, = 1.4468 RuF = R Fj F(P,T,Z,RH) = radio frequency refrac- tion model K, = 0.25391 P = pressure K, = 2.2716 T = temperature K7 =1.34G5 Z = zenith angle Ka = --4.3877 RH = relative humidity & = 3.1484 N(h) = ND(h) + NW(h) KI, — 4,5201 N(h) = total refractivity at radio frequencies i K, 1 = --1.89$2 ND(h) = dry, or optical component, of refractivity K., T 0.89000 NW(h) = wet component of refractivity P = pressure, mm Hg h = height P,, = 760.00 mm Hg ho = station height A; = 0.40816 s = parameter surface value A2 = 112.30 ND(lao) = ND, T = temperature, kelvins NW(hp) = NWT To 273.00 K N(ha) = N. B, = 0.12820 In general, attempts toconstruct a radio frequency B^ = 142.88 refraction model consisted of appropriating an empirical model from optical refraction work which would give theQ, = 91.870 functional dependence on Z (say Rz(Z)), and then scaling C, = 0.80000 this expression. by the total. radio frequency surface T refractivity, i.e., C $9 344 refraction N.. Rz(Z) CN f'More pertinent for use at JPL, however, would be antgular refraction model which would possess very high where N T = reference optical refractivity. tccuracy at S- and Y band (radio) frequencies. At the ime, it was hoped that a reasonably accurate .method.. At this point, one must ask,. what are the implications . ;ould be found to transform the optical refraction. model of this procedure? Since any signal (that is of interest p a radio-frequency refraction model. Past attempts to here) must` traverse the entire troposphere, and. is of iccornplish this will be dealt with first, and then a new course, continually being refracted, one might think that nethodto accomplish the transformationwillbe proposed. instead of being .proportional to surface refractivity, angu model by the total surface radio refractivity to achieve a radio angular refraction model would appear to be seri- ously flawed. III. Method Used to Transform From an Optical to a Radio Frequency Refraction Model From the previous section it was seen that RxF, cc N, = ND, + NW, is a poor choice. A more Iogical choice would be RHr cc f N(h) dh = f {ND(h) + NW(h)) dh f ND(h) dh + f NW(h) dh = f ND(h) dh 1 + f NW(h) dhf ND(h) dh Similarly, for the optical case (using the model previously presented): Ror cc f ND(h) dh Combining the above, one arrives at the equation that will be used for the radio frequency angular refraction model: Rx,(P,T,Z,RH) -- R,,-(P,T,Z) I, + f NW(h) dhf ND(h) A 1V. Determination of Ratio of Integrated Wet Refractivity to Integrated Dry 3 Refractivity In attempting to determine an analytical parametric representation for the expression: f NtiW(h)dh f ND(h) dh The most.difficult problem by far lies with the integrated wet refractivity. Berman first showed in 1970 (Ref. 2) that RRx (ND, + NW,) R,(Z) f ND(h) dh = AP, R ^ND,^^ g However, it is well known that wet refractivity "decays" %%-here much more rapidly than dry refractivity (for instance, A = 77.6Ref. d), so that f,(h) and f..(h) are quite . dissimilar; thus, the procedure of scaling an optical angular refraction P, = surface pressure; mbar lar refraction is really more nearly proportional to total (integrated) tropospheric refractivity, i.e., Refraction cc f N(h) dh However, refraction could also be proportional to surface refractivity if it could be assumed that there exists some f (h) such that: N(h) = Nxf(h) so that refraction x f N,f (h) dh = N. f f(h) dh Making the assumption that ND(h) , ND, f,(h) NW(h) — NW, f 2(h) . one would have for the optical case: Rz °c f ND(h) dh = f ND, f,(h) dh = ND, f f,(h) A For the radio frequency ease: Rtnp x f N(h) dh = f {ATD(h) + NW(h)} dh = f (ND, f,(h) + NW, f.^(h} } cila = NDR f f,(h) dh + NW, f f.(h) dh Without precise knowledge of the form of f,(h) and f :!(h), the only way that the surface refractivides could be used to transform from the optical case to the radio case would be if fi(h) f (h) Then. RsF cc (ND, +IOW,) f f,(h) dh and indeed 144 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 iR = perfect gas constant g = gravitational acceleration g/R = 34.1'C/km and also gave an expression to approximate the inte- grated wet refractivity: f NW(h) dh = C C,C,(RH)„ ^I — T AT,, I — B I I B—A{; e^^ To—C } where C, = 77.G C2 = 29341.0 RH = relative humidity y = temperature lapse rate C = 38.45 TQ = extrapolated surface temperature A = 7.44751n (10) B = 2034.28 In (10) Chao (Ref. 5) later improved upon the integrated wet refractivity with the expression: f NW(h) dh = 1.63 X I0= { eT ,M1 + 2.05 X 10 2 a'r ttt fl 1 n 11 where e„ = surface vapor pressure, N/m= To — surface temperature, K a = temperature lapse rate, K/ km However, both of these expressions depend upon one or more parameters not measurable at the surface (i.e., temperature lapse rate, etc.), and neither is particularly accurate. Going back to the previous section, if the altitude-dependent refractivities could really be. repre- sented as ND(h) --- ND,f 1(h) NW(h) NW, f.-(h) and if the above refractivities could be integrated, i.e., if A below could be evaluated as A = f f2(h) d1z f f,(h) dlr then one might simply expect that f NW(h) dh NlV' f ND(h) dh A ND. To test this hypothesis, the authors had ten cases used in Ref. 2. Although a very small number, the cases were alternate day and night profiles selected throughout the year (December, February, April, August, September). A least-squares linear curve fit to the above data was per- formed as follows: f NW(h) dh NW, 1 f ND(h} dh ' A 17N D.f The fit yielded the following: A = 0.3224 Q( %) = 00.93% x[Q(%)=I00X (fNW(h)d1, ^VW„fN—AND^^ Translated to centimeters of integrated refractivity, one would have Q(cm) = 2.0 cm Table 1 and Fig. 1 present the detailed analysis of the ten cases described. As a totally independent check of this observed rela- tionship, use can be made of work done by Chao (Ref. 4) on wet and dry refractivity profiles. Combining Eqs. (9), (10), (13), (14), (15), and (16) from Ref. 4, one has: ND(h) = ND, 1 — Ia . 4 C .? L.2 km 42.7) — ( `^'} 69 ND, ^exp ^— 1a 6.4M } h > 12,2 km ra NW(h) = W, [ 1—` 1 } h _C. 131, - — 0 h ? 13 krn JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 145 {Performing the dry refractivity integration, one has Or, finally r ND(h) c11i r 1 - ND,, (1- 4 L7 } ` d1i. ^W ND(h) A— ND,(6.952) + m 70 ND ea (h — 12.2) dh " { T ^— + a^^ ND,(6.4) 269 6.4 = 8.6174(ND„) r ` 71 7)y AND8 J ^^ ^(1 -- ^ " \ Performing the .vet refractivity integration, one has R + 2 9 ND exp _ (It G.42 2) clla NW(h) A = NW, { 1— h dh f It l \transforming the first integral by r N dh— W, ^ l --1 o 'a 13)a _ h 1 2.7 Transforming the integral by dh = —42.7 dx so that _ 1^ — xl 1 13^ '1 — 49 7 } dh = — 42.7 f x; clx dh = —13dx 42.7 s (I ^ iI dh = —13 f x4 dxf — _ 42.7 — la _._ 42.7} ]°5^ — —13 = 6,952 5 ^ 11 13^J1°3 Transforming the second integral by = 6 (h — 12.2) so that— — 6.4 dh = —6.4dx pJ NW(h) dh = 2.6(NW$) u so that Combining the integrated vet refractivity and the inte. (it —12.2) grated dry refractivity yields. exp 6.4 dh = 6.4 f exp (x) dr _ — 6.4 exp O J NW(h) dh° 2.6(N.WB) r _ (it — 12.2) — —6.4 I exp 6.4 8.6174(NDg)f ND (h) A = 6.4 NIV.N0.30].72 _ ND,, 1 146 JAL DEEP SPACE NETWORK PROGRESS REPORT 4225 ^. I I k {i 1 :i F :f This is to be compared to the previously determined V. f=inal Angular Tropospheric Radio relationship from actual data of: Frequency Refraction Model ' rr The following gives the complete radio frequency 3 f N117(h) dIa angular tropospheric refraction model: 0.3224 nr^ N D. lV ND(h) cIlt ^ p J r Since the value of the la standard deviation t R = F,,r f FTC exp o - ° 1 .oa{Z) ' K„ E 1er = 00,93% (, _ 2 cm) i P1 A,(P,Z) ^ F, - _ . 1 + A,(Z) found from actual data compares favorably with the most recent modeling published by Chao in Ref. 5 (r3 cm for T, A^(T,Z) . combined night and day profiles), and since the basic rela- F _^ — x l 1 T A:,(Z) tionship seems verifiable by average profiles presented by Chao; the determined expression will be adopted for use / W„RH W,T — W- with the optical refraction model. The surface refractivity _F,° — (1 + TP e\\ T — W,(Ref. 2) is defined as: A l(P,Z) _ (P _.. P.) {exp IA,(Z — A:)])(RH)„C,C: AT„ BNW8 = Tn eV T8 — C A^(T,Z) = (T — T,,) {exp [B,(Z — B-)] ) ND„ = C, T Aa(Z) = (Z — CE,) {exp {C,(Z — C2)1}} so that one would obtain where n R = refraction, see f NW(Ii) A. (RII)'C2 rATx — B Z = actual zenith angle, deg1+ F ^1 , 0.32.14 ex ( 1f ND(h) dlt M E { ^) T"P" \ T^ — C J^ EL = elevation angle EL= 90 deg — Z To integrate this expression into the optical model, the 7. _ KIpressure term must be converted from mbar to mm: U(Z) K: f P& (mbar) = P,,(mm) X K, = 46.6780 K= -- 45.375 so that one would finally have K, = 4.1572 fl + f NW(h) Al 1 F (7.1 X 103) (RH), e, f ATR_ B^ K; = 1.4468ND(h) U — , p TK—Cf (} K, = 0.25391 1 t where K, 2.2718 (RH)p = surface relative humidity (100% =1.0) K, =1:3465 . T$ = surface temperature, K Ks = -4.3877 Pe = surface pressure, mm of Hg K,, - = 3.1484 A = 17.149 K,o = 4.5201 B = 4684:1 K„ = --1.8982 v C T 38.450. K,z = 0.89000 !PL DEEP SPACE NETWORK PROGRESS REPORT 42-25 147 aI P = pressure, mm Hg Po = 760.00 mm Hg Al = 0.40816 A3 = 112.30 T = temperature, kelvins T„ = 173.00 K B i = 0,128-20 B2 = 142.88 C„ — 91.870 C, = 0.80000 C2 99.344 RH = Relative humidity (100% = LO) Wo=7.1X103 Wl = 17.149 W2 = 4684.1 W;, 38.450 V1. Model Accuracies The inaccuracies introduced by the wet refractivity term predominate over the inaccuracies presented in Ref. 1. Considering 1a = 1.00% the maximum la angular errors would be Z, deg AR, see AR, deg 0-85 6 0.002 85--90 IS 0.005 90-93 50 0.015 V11. Fortran Subroutines Reference 1 presented two Fortran subroutines, cor- responding to the full optical refraction model and an abbreviated version. These two routines have been trans- formed to the radio frequency version of the refraction model, and are presented in Appendixes A and B. The Fortran subroutine SBEND (Appendix A) represents the full model, while XBEND (Appendix B) gives the abbre- viated version. Inputs required are: PRESS — pressure, mm of Hg TEMP = temperature, K HUMID = % of relative humidity (100% = 1.0) ZNITH = actual zenith angle, deg and the subroutines return with R = refraction correction, see i JPi. DEEP SPACE NETWORK PROGRESS R References 1. Berman, A. L., and Stockwell, S. T., "A New Angular Tropospheric Refraction Model' in The Deep Space Network Progress Report 42-24, Jet Propulsion Laboratory, Pasadena, Calif., Dec. 15, 1974. 2. Berman, A. L., "A New Tropospheric Range Refraction Model' in Space Pro- grams Summary, No. 37-65, Vol. 11, pp. 140-153, Jet Propulsion Laboratory, Pasadena, Calif., Sept. 30, 1970. 3. Ondrasik, V. J., and Thuleen, K. L., "Variations in the Zenith Tropospheric Range Effect Computed From Radiosonde Balloon Data" in Space Programs Summary, No. 37-65, Vol. I1, pp. 2545, Jet Propulsion Laboratory, Pasadena, Calif., Sept. 30, 1970. 4. Chao, C. C, "New Tropospheric Range Corrections With Seasonal Adjust- ment" in The Deep Space Network Progress Report, No. 32-1526, Vol. Vi pp. 67--73, Jet Propulsion Laboratory, Pasadena, Calif., Dec. 15, 1971. 5. Cbao, C. C., "A New Method To Predict Wet 'Lenity Range Correction From Surface Measurements" in The Deep Space Network Progress Report, No. 32-1526, Vol. XIV, pp. 33-41, Jet Propulsion Laboratory, Pasadena, California, April 15, 1973. 1 1 `. Table 1. Surface refractivity vs integrated refractivity A 0.3224 0 0.93% NW NW JNW(h) A 100 X A X f100 X °t 100 X Case rrrr11 ND ND8 f ND (h dh (°Ia) A; cmW Rl(%0) M 1 4.86 1.57 2.27 -x-0.70 +1.48 2 3.76 1.21 2.17 +0.96 x-2.03 3 5.74 1.85 1.80 -0.05 -0.11 4 5.34 1.72 1.37 -0.35 -0.74 5 4.74 1.53 1.75 +0.22 +0.47 6 7.14 2.30 2.17 --0.13 --0.28 7 24.11 7.77 8.55 x-0.78 +1.65 8 31.72 10.23 9.12 -1.11 -2.35 9 7.29 2.35 4.58 +2.23 x-4.72 10 9.89 3.19 2.69 -0.50 -1.06 k I ^` 1 r 1 ^ 1 10 r 8 S n ^ 5 a s_ 3 4 Z. 0o z a ity Appendix A Subroutine SBEND 00101 1* SUBROUTINE SBEND(PRESS&TEMP,HUMID,ZNITH,R) 00103 2* DIMENSION A(2) ► B(2),C(2)#E(12),P(2)PT(2),Z(2) 00104 3* P(1) = 760.00 00105 4* T(1) = 273.0 001.06 5* Z(1) = 91.870 00107 6* P(2) = PRESS 00110 7* T(2) = TEMP 00111 8* Z(2) = ZNITH 00112 9* A(1) = .40816 00113 10* A(t) = 112.30 00114 11* B(1) = 912820 00115 12* B(2) = 142.88 00116 13* C(1) = .80000 00117 14* C(2) = 99.344 00120 15* E(1) = 46.625 00121 16* E(2) = 45.375 00122 17* E(3) = 4.1572 00123 18* E(4) = 1.4468 00124 19* E(5) = .25391 00125 20* E(6) = 2.2716 00126 21* E(7) =-1.3465 00127 22* E(8) =-4.3877 00130 23* E(9) = 3.1484 00131 24* E(10)= 4.5201 00132 25* E(11)=-1.8982 00133 26* E(12)= *89000 00134 27* w0 = 7100.0 60135 28* wl = 17.149 00136 29* w2 = 4684.1 00137 30* M3 = 38.450 00140 31* D3=1.+DELTA(Z,C,Z(2)1 00141 32* FP=(P(2)/P(1))*(l.-DELTA(P,A,Z(2))/D3) 00142 33* FT=(T(1)/T(2))*(1.-DELTA(T,BPZ(2))/D3) 00143 34* Fw=1+(MO*HUMID*EXP((wl*T(2)-M2) /(T(2)-Y3)) /(T(2)*P(2))) 00144 35* U=(Z(2)-E(1))/E(2) 00145 36* X=E(11) 00146 37* DO 1 I=1*6 00151 38* 1 X=E(11-I)+U*X 00153 39* R=FT*FP*Fw*(CXP(X/D3)-E(12)) 00154 40* RETURN 00155 41* ENO 00101 1* FUNCTION DELTA(A,B,Z) 00103 2* DIMENSION A(2),B(2) 00104 3* DELTA= (A(2)-A(1)) *EXP(B(1)*(Z-B(2))) 00105 4* RETURN 001.06 5* END I 152 JPL DEEP SPACE NETWORK PROGRESS REPORT 42.25 Appendix B Subroutine XBEND 00101 SUBROUTINE X8END(PRES59TEMPvHUMl0vZNITH.RI 00103 20 DIMENSION E(12) 00104 3• P w 760.OU 00105 40 T • 273.00 UOI04 50 E(I) E 46.625 00107 60 E(2) n 145.375 00110 7* E(3) • 4 *1572 00111 8• E14) n 1.4468 00112 9• E(S) w 925391 00113 10s E(6) • 2.2716 00114 lie E(7) •1.3465 O011S 12ft E(8) n .493877 OC116 130 E(9) n 3.1484 00117 146 E1101 n 4x5201 00120 150 E(11).-1.8982 00121 160 E(12)m •89000 001 2 2 179 w0 • 710090 00123 18• wl . 179149 0012 4 19• w2 • 4684.1 00125 200 w3 w 389450 OO126 210 FP n PRESS/P 00127 22• FT n T/TEMP 00130 23+ FW n I **D*HUMID•EXPIIWI•TEMP-*21/(TEMP +w311/(TEMP•PHESS) 00131 24* U.(2N1TH-E(1)) /E(2) 00132 250 X n E(Il) 00133 269 00 1 I.1l6 00134 270 1 X.E(ll-l)•U•X 001 4 0 28e RaFTOFPoF**(EXP(X)wE(12)1 00141 29• RETURN 001 4 2 300 END JPL DEEP SPACE NETWORK PROGRESS REPORT 42.25 153 i E I I' 1 A .Nevi Approach to the Evaluation and Prediction of 'het Tropospheric Zenith Flange refraction A. L. Berman 1 Network Operations Section The best.current model for predicting; icet tropospheric zenith range refraction exhibits an uncertainty of approximately 3.0 cm (1a). This report presents an approach that has the potentiality of reducing the uncertainty to the range of approximately I.5 to 2,0 cm (1a). Furthermore, the current model requires both surface parameters as well as tropospheric parameters, while the approach dealt with in this report requires only surface parameters. z I L Introduction where The last five years have seen a substantial effort at the AR„ = wet zenith range refraction (cm) ,let Propulsion Laboratory to evaluate and, hence, be able to predict zenith range refraction. Determination of the NW(h) = wet component of refractivity dry component of range refraction is quite straight- It = height above observer (km)forward; therefore, most activity has been expended in attempting to develop accurate methods to evaluate the C, = 77.6 wet component of range refraction. In 1970 this author Cl... 29341.0proposed. a model based on the assumption of constant relative humidity as follows (Ref. 3): RH = relative humidity (100%n = 1.0) y - temperature lapse rate (KA-M) R„• = 10-1, f NW(h) dh C = 38.45 T,, = extrapolated surface temperature, K } A = 7.4475 (In 10)C' C=C-(RH3d ^ (; - p l t AT¢ — B^ n nnni nn ^Y4 n m This model exhibited a standard deviation of approxi- mately: 1d 4.0 cm In 1073, Chao (Ref, 6), assuming an adiabatic atmo- sphere model, improved upon the evaluation of wet zenith range refraction with the following expression: / es.za 10-$ f NW(h) dh = 1,63 X 10 2 } 0 TO + 2.05 X 10-'a ° ^a o where e„ = surface vapor pressure, N/M2 T„ = surface temperature, K a = temperature lapse rate, K/lm This model produced a standard deviation for combined day and nigh t cases of la 3.0 cm The uncertainty in even the Chao model is large, however, when compared to an average wet zenith range refraction of approximately 10 cm; thus efforts to improve upon this model would not be entirely academic. 11. New Approach to Evaluation of Wet Zenith. Mange Refraction In the course of developing a new radio frequency angular tropospheric refraction model (Ref. 1), it was found necessary to evaluate the ratio of vet zenith range refraction to dry zenith range refraction. Letting N(h) ND(h) + NW(h), the total refractivity at radio frequencies NW(h„) = NW N(hn) = N, and defining AR, = 10- f ^NW(h) dh O AR„ = 10- 1, f O'ND(h) dh n It was necessary to determine some f such that: f mNW(h) dh _ ARu, _ U f - .BRA r T* ND(h) dh4 It was empirically found that there existed strong cor- relation between the ratios of wet and dry zenith range refraction and of vet and dry surface refractivity, i,e. that AR,i K C NWa f ARI, ND, with K= 0.32. There is an immediate implication that, if indeed there existed strong correlation, then this (assumed) .relation- ship might be useful in predicting wet zenith range refraction. AR„- NW, AR, K CND, then If 7 7 i oR„ aRD • K C ND, (Nw',) ND(h) = dry or optical component of refractivity Defining NW(h) = wet component of refractivity C, . = 77..6 It = height C_ = 29341.0 h„ = observer height RH = relative humidity S -- parameter surface value R = perfect gas constant ND(h„) = ND, g = gravitational acceleration JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 155 1 ' I 1 t g/R = 34.1 ° C/km P = pressure T W temperature s = surface parameter value A = 7.44751n(10) B = 2034.28ln(10) C = 38.45 one would have from Ref. 3: R OR'(cm) = (10-1) Cl P. g ND. = C1. P.^. Cf C2 (RH)& / AT, — S NMI. _ — Xp l -CTa e T. so that The above expression is simpler than those referred to previously, and more significantly, it is only dependent upon surface parameters, unlike previous expressions that depended upon one or more tropospheric param- eters not directly measurable from the ground. In 1970, J. V. Ondrasik considered a very similar approach, that is, correlating zenith wet range refraction with surface wet refractivity (Ref. 4, P. 34), i.e., aR„• .- Y.. (NL'VA) -1- K, but (apparently) dropped the idea as unpromising. Table 1 presents a detailed listing of 10 selected atmo- spheric cases previously described in Refs. 1 and 3. The standard deviations described in the table are as follows: oR^, Cr(cm) = a aRjv — K C NDa NWa , cm aR,y W, a(%) = 100 X a- QRn — K [E— ND, ^^ The results of a least-squares curve fit of these 10 cases to: r RA ^R "'; K NU^^ (I0-1) C, PR 1 yieldedL g oR,y K K = 0,3224 T. "(cm) ~ 2.0 cm Cl C, (R11). AT, — B X T2 exp T. _ C This data can also be seen in Fig. 1. B As a check to the basic procedure, use was made of R T, C, C: (RH)a AT - B data presented by Ondrasik in 1970 (Ref. 4, p. 34, Fig.K g(1D) T= e Ta - C } 11). Although this data consists of 18 R Cl C2 (RH); AT, — B AR„. vs NW, K eg (10) Ts { T,- C / the process of predicting now ARS, K NW, R C1C2 (77.6)(29341:) _ — 6677.0 should yield a substantially similar uncertainty. Using theg (10) 34.1.:... average integrated wet refractivity relationship derived so that finally in Ref. 1 (and based on work done by Chao, Ref. 5), i.e., [ 6677.0 AT. - B Dll,v K(RH), exp 10-° f NW(h) dh ,~ 0.26 NW,j cm .Tn 1,A n ]5fi JPi. DEEP SPACE NETWORK PROGRESS REPORT 42-25 yielded the following standard deviation: 1Q = 1,,(AR,,. — 0.26 NW,) 2.3 cm which is at least a similar number to that uncertainty obtained from the proposed procedure. Ill. Consideration of the Differences in Day and Night Wet Refractivity Profiles It has been suggested here that there exists a strong (empirical) relationship between integrated wet refrac- tivity and stirface wet refractivity: [1R„, K E N61 I NW, Since there is Iittle dynamic variation in the term (AR,,/ ND,), the above relationship implies an "average' wet profile, say fA %. ,(h), such that A, R„• = 10-'° f aNW(h) dh 0 10-1 f NNW., f,,,,(h) dh 0 10 f m f •,,,.(h) dh NW, 0 [K ^±R ND, ^] NW, The main considerations which detract from an "average” wet refractivity profile are fluctuations in rela- tive humidity: The conclusion one expects is that the K (= 0.3224) previously determined would be larger for night only profiles and smaller for day only profiles. This in fact turns out to be the case. The data previously analyzed was separated into day only and night only profiles, and yielded the following results: Day profiles K = 0.2896 U(cm) = 1.1 cm Night profiles K = 0.3773 U(cm) = 1.9 cm This data appears in Table 2 and Fig. 4. IV. Adjustment of Surface Temperature to Reflect Differences in Day and Night Profiles In the previous section it was pointed out that syste- matic diurnal surface temperature variations cause systematic distortions in attempting to fit total wet zenith range refraction to surface wet refractivity. As a final attempt to explore ways to account for this effect the following was tried: Let Th,,, = lowest previous 24-h temperature = highest previous 24-h temperature Then, to moderate the night and day profile distortions define: RTI(h) =A (RH), 3Tn1N + Ttaax T(night profiles) = and near surface variations in temperature. Whereas the 4 fluctuations i% relative humidity appear very random, 3Tuex 'f' Turnthe variations in surface temperature are much more T(day profiles) — systematic and. can. be characterized as either day or 4 night type profiles. A typical appearance of night and day temperature profiles is shown in Fig. 2. Entering these temperatures into the previously de- scribed cases yielded If one assumes an "average' wet refractivity profile, K = 0.3281 then obviously using a "night" NW„ will give too small a total wet zenith `range refraction; conversely, using a a(cm) = 1.3 ern "day" NW, will lead to too large a total wet zenith range refraction. This can be seen in Fig. 3. The results can lie seen in.Table 3 and Fig. 5. . JPL DEEP SPACE [NETWORK PROGRESS REPORT 42-25 157 IV. Conclusions Depending on how the equation is used, it appears to From the (admittedly} small data set at hand, there potentially yield an uncertainty in total wet zenith range refraction of appears to be a strong correlation between total wet v(cm) ^' 1.5 to 2.0 cm zenith range refraction and wet surface refractivity, in the form of Also, it possesses the advantage of tieing dependent on surface parmneters only, in contrast to previous methods. _ oRp Table 4 presents a comparison of previous results eon-Rzi — K C ND, NWT trasted to results from the proposed procedure. Obviously, however, a much larger data set wou?a have to be = K(RH)a C 6677.0 exp ATe — B analyzed before the results presented ir, t;aiil report could L Tp Ta _ C be verified and accepted. References 1; Berman, A. L., aid Rockwell, S. T., "A Proposal for a New Radio Frequency Angular Tropospheric Refraction Model For Use Within The DSN," IOM 4916 74321, Dec. 5, 1.974 (JPL internal document). 2. Berman, A. L., and Rockwell, S. T., "A New Angular Tropospheric Refraction Model," in The Deep Space Network Progress Report 42-24, Jet Propulsion Laboratory, Pasadena, Calif., Dec. 15, 1974. 3. Berman, A. L., "A New Tropospheric Range Refraction ModeI," in Space Pro- grams Summary, No. 37-65, Vol. II, pp. 140. 153, jet .Propulsion Laboratory,. Pasadena, Calif., Sept. 30, 1970. 4. Ondrasik, V. j., and Thuleen, K. L., "Variations in the Zenith Tropospheric Range Effect Computed From Radiosonde Balloon Data," in Space Programs Summary, No. 37-65, Vol. II, pp. 25-35, Jet Propulsion Laboratory, Pasadena, Calif., Sept. 30,1970. 5. Chao, C. C.,. "New Tropospheric Range Corrections With Seasonal Adjustment," in Deep Space Network Progress Report, No. 32-1526,Vol. VI, pp. 67-73, Jet Propulsion Laboratory, Pasadena, Calif., Dec. 15,1971. 6. Chao, C. C., "A New Method to Predict Wet Zenith Range Correction From Surface Measurements;" in The Deep .Space Net-work Progress Report, No. 32-1526, Vol. KIV, pp. 33--41, jet Propulsion Laboratory, Pasadena, Calif., April 15,1973. Table 1. Surface refractivity vs Integrated refractivity (A = 0.3224, a = 0.93%) fNW (h) dh Case NW8 100- ND , % ( NW8 ) A X 100 X ND J}, l°Ir) l0A X fND (h) A ( %.) 0 (%a) A.() 1 4.88 1.57 2.27 4.0.70 -}-1.48 2 3.76 1.21 2.17 +0.96 •{-2.03 3 5.74 1.85 .1.80 -0.05 x-•0.11 4 5.34 1.72 1.37 -0.35 -0.74 5 4.74 1.53 1.75 +0.22 -1-0.47 6 7.14. .2.30 2.17. -0.13 --0.28 7 2411 7.77 8.55 40.78 +1.65 8 31.72 10.23 9.12 -1.11 -2.35 9 7.29 2.35 4.58 +2.23 -1-4,72 10 9.89 3.19 2.69 -0.50 -1.06 i Table 2. Surface refractivity us integrated refractivity j NW ( NW fNW(h) dh. Case 100 X ND8 A X { 100 X ND, 1QQ X fND(h) dh (°!a) (cm) Day profiles ( even) A = 0.2896 u = 0.501/1c, j 2 3.76 1.09 2.17 -1.1.08 42.29 4 5.34 1.55 1.37 -0.18 -0.38 6 7.14 2,07 2.17 -1-0.10 +0.21 8 31.72 9.19 0.12 -0.07 -0.15 10 9.89 2.86 2.69 -0.17 -0.36 Night profiles (odd) A = 0.3773 a = 0.89% 1 4.86 1.83 2.27 +0.44 +0.93 3 5.74 2.17 1.80 -0.37 -0.78 5 4.74 1.79 1.75 -0.04 -0.09 7 24.11 9.10 8.55 -.0.55 -1.16 9 7.29 2.75 4.56 -1-1.83 +3.87 JPI- pEL".P SPACE NE7WORK PROGRESS REPORT 42-25 ^ ^ 159 Table 3. Surface refractivity vs integrated refractivity A=0.3281 a =0.63% NWBa NWsn f1VW I dh i.Case 100 x ND. A x 100 X ND, 100 x f^+, Dlm) dh A (`^a) A (cm) 1 8.43 2.11 2.27 +0.16 -1-0.34 2 2,92 0.96 2.17 +1.21 +2,55 i 3 7.18 2.36 1.80 --0.56 -1.18 4 4,45 1.46 1.37 -0.09 -0.19 5 6.19 2.03 1.75 -0.28 -0.59 6 5.61 1,84 2.17 -0.33 -3-0.70 7 26.43 8.67 8.55 -0.12 --0.25 8 29102 9.52 9.12 -0.40 --0.84 { 9 9.83 3.23 4.58 +1135 +2.85 .i 10 7.70 2.52 2.69 +0.17 +0.36 i ^n"Modified" surface temperature in calculation of NW,, l Table 4. 1c Uncertainties in wet zenith range refraction Data source Ref. 3 Ref. 6 Proposed Approach K 0.2890 Modified surface °Model Berman 1970 Berman 1970 Chao 1973 K - 0.3224 K, = 0,3773 temperature. i Day profiles 1.5 em 3 .5 cm 2 .0 em - 1.1 cm - Night profiles 5.5 cm 4.9 em 4. 1 em - 1.9 cm - Composite 8.5 cm 4 .2 cm 3 .0 cm 2 .0 cm 1.5 cra 1.3 cm 3 160 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 I i 10 O S 8 s O z b A = 0.3224 sa s 0 3 4 z 0 O 2 00 0 0 0 10 20 30 DAY NW, 100 (NWs/N qs) ` DAY NW, NW ` WITH "AVERAGE" Fig. 1. Integrated refractivity vs surface refractivity, A = 0.3224 ` PROFILE NIGHT NWS { f 1 0i J i 0 10 20 30 100 (NW,/ND,) 3 Fig, 4. Integrated refractivity vs surface refractivity, A = 0.3773 and A = 0.2896 4 . s °a i ]0 O 8 Doppler Phase-Noise Measurement Using Mean-,Sweep Techniques R, C. Bunce Network Operations This paper describes an investigation leading to techniques to reduce the error present in the DSN station measurement of doppler phase-noise variance and standard deviation. The error source of concern is the doppler counter resolver, which sorts continuous phase data into finite group intervals. The intervals are 3.5 deg (1 MHz bias) or I8 deg (5 11Hz Bias) wide. Counter operation is covered to define parameters, and then appropriately limited model functions for the variance, its estimate, and the error are stated. The model introduces linear and sinusoidal mean-sweep functions to investigate their effect on the error. Machine-programming of the model yields results which indicate that mean- sweep significantly reduces the measurement error tchen phase-noise standard deviation is loco (less than 2 deg at 1 1fHz bias, or 10 deg at 5 MHz bias). Linear sweep is the most accurate technique, but sinusoidal sweep is recommended as the more feasible; errors with the latter do not exceed 0.15 deg rms (1.0 MHz bias) in the region of interest. Finally, the recommended parameters and the expected residual error are stated for use in test program configuration and data reduction; the error is. asymptotic to a universal constant variance offset which can be appropriately subtracted to compensate for the group interval tziath at all noise levels. Introduction Present doppler phase-noise measurement tecluiiques yield reasonably accurate estimates When the noise standard deviation (sigma) exceeds 2 deg rms (1.0 Iv1Hz bias) or 10 deg (5.0 11Hz bias). However, when sigma is smaller than these values, the estimat obtained is in- creasingly variable with certain initia: conditions, be- coming practically meaningless below 1.0 deg (1.0 MHz bias) or 5.0 deg (5:0 1•iHz bias). Sigma levels x0thin these regions are encountered in strong-signal coherent S-band test modes and X-band operations and test procedures. JPL DEEP SPACE NETWORK PROGRESS REPORT 42.25 163 iAn initial condition of interest in this region arises from the finite tine-resolution of the doppler counter resolver. The resolver estinikes the time-position of waveform zero-crossings, which form a continuously distributed set when random noise is present. The mean value of this scat is, howeve r, stationary Lvith respect to adjacent resolver pulses when these pulses are tirne-coherent with the bias period, the usual test case. The time difference between the inean-value zero-crossing and the adjacent (earlier) resoivcr pulse, its estimate, is an error variable with initial conditions and cannot normally be predicted. As this initial offset varies, the final estimate of sigma varies. When sigma is small, this variation is too large to yield meaningful neasures with confidence. However, if this initial offset is intentionally varied by a known "mean- sweep" function during data collection, the error will tend to average, and the total possible variation will presum- ably decrease. The following discussion investigates this possibility in detail by modeling the resolver behavior during application of various sweep forms. 11. Doppler Counter Operation and Measurement Model Doppler phase-noise measurement in the DSN stations is done by processing a set of doppler counter samples, Reduction of this data set yields an estimate of random phase-noise variance u20 and/or standard deviation rsq. The latter is simply the rms value of the noise. The variance and standard deviation depend on signal strength, mode of operation, system temperature, system noise, and many other factors. Doppler noise standard deviation is as low as 1 or ? deg or less under strong-signal coherent. conditions, when system noise is minimized. The actual noise data extracted from the counter sam- ples is a residual on the order of 1 X 10-" of the phase accumulation between samples. The total differential phase between each sample is primarily the counter bias phase-accumulation over the sample period r. The ac- cumulation is normally between 1&- cycles and W; cycles, depending on the period- and the bias frequency B. At the end of each sample period, the accumulated total cycle count (since reset) is read out as in integer, The readout is not the differential phase, the counter acts as a continuous digital integrator, summing these differen- tials. In addition, the counter is mechanized to obtain meaningful residual data by means of . a resolver that measures (each sample period) the time position of the final waveform (positive-going) zero crossing of the period, within a resolution of 10 ns (A-0. The resolver tabulates the number of 10-ns intervals, an integer K. This integer is also read out and understood as an estimate( Ka,) of the true resolver period AT between the timing pulse that ended the sample period (t,,) and the time of the final positive-going zero crossing (t.). The period KAT is not precisely equal to AT, and thus is not correct, for the tabulation is stopped at l., whieli normally occurs at some point between discrete resolver increments KaT and (K >- 1) AT, Expressed quantitatively, t. = t,, , AT = t„ + KAT - ST 0 < ST < AT (i} where AT = true time inereinont from tr, to the zero cross- ing t. Ar fixed resolver tune increment, 10 ris ST = error of Ka-, in measuring AT K ^ resolver increment index or count The quantity of interest is the residual phase 01, which is the (accumulated) diffe =rence between the true p'- ►ase and the nominal please due to bias alone, This can be expressed as a frequency integral yielding the integrated integer I described above: f^ ^T I =[B — ^, )j dt r„ t^+]T B[(tn — t„) —1 aTj - r ^,(t dt =B[(t,,—t) AT]_ $x where t., time of first zero crossing after reset. The nominal, due to bias alone, is r.,.,rn I„ =B dt = B[(t,; — t„) AT,1f, where t„ is repeated; the start tune is theoretically irrelevant. Or 164 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 1 E tI E ^ (I — Iu) = al = B[ AT — AT.,] — Oil ^H = J ` ^,(t) art Although actual mechanization restricts AT to a range of values, with small differences of Ar completing the relationship, it simplifies the model, without loss of gen- crality, to assume I and I„ equal, with AT having com- plete freedom. This lead to ¢art = B [AT — AT,] B[KA-, — KAT] + B[ST — ST,.] (2) By similar development, the estimate of og, 0"x can be shown to be ¢a rc B[(K -- IG.) AT] .. rr +liar +6T = ^k -- (S¢ — S^„) -I- ^ ^rr(t} clt {3} fp +her The integral is considered negligible; residual fre- quency components are too small to build up any appreciable value over the short time span. This yields (in parallel «rith olr) n err = B[K — K..] aT = oil — B(ST — ST..) These stable forms allow a convenient scaling; it is to set K,.' = 0 (shift the index origin to K,) and simultane- ously define the phase of the set of resolver levels Ori by the notation OK = KAO - &P ” (4) where K = --2, —1, Q, 1, 2, . . — :c C OR C + x The residual phase argument ¢rr consists of all devia- tions from nominal bias phase. To further limit the discussion, consideration will be given to only two con- tributions; all others will be assumed negligible. The two are- (1) Intentional, known, and deterministic deviations of the true mean from the nominal (bias) mean. (2) Random phase noise, as-mmed stationary, gaussian, and normally distributed, with variance a^, With these, 0,l. becomes Orr = ^ 4,. 0 where intentional mean displacement of the entire 0 distribution from nominal = phase-noise displacement from ; at any instant of measure The phase quantities above and. their time equivalents are diagrammed in Fig. 1, with a superimposed typical phase-noise probability density function. Note the actual measure 0 at time t, occurs between resolver levels 0, and 0.;: The (index-shifted) resolver readout would be the °K' index of CA4, equivalent to KA¢ of ¢ri, or "4," and any zero-crossing in the shaded area A, would yield this read- out. The area A, thus represents the probability of the reading 4.10; other area probabilities would occur similarly. After observation of Fig. 1, it becomes apparent that the various probability areas, such as A., shown; vary for given oK if the mean dimension ¢ is varied, and that this will certainly not degrade the data if the mean variation is known. 84, = BST, = the offset of mean ¢x from the nearest lower resolver level The effect of sweeping is actually to vary the location of all P(0) with respect to the {¢ A ). Various initial So. These combine to will thus obviously alter the result, since the ¢ h are a. function of 5o,,. In fact, the purpose of mean-sweep is to _ eliminate or reduce the error due to arbitrary initial un- ^>t + Sr¢ known Sip,, with a compensating, known, and averaging bR = OK + So„ = KAo .. (5) function_ where aq, = BAT = 3.6 deg (1 MHz) or 18 deg (5 MHz) and JPL DEEP SPACE NETWORK PROGRESS REPORT 42-25 165 jAt the extreme, without sweep, if the entire P(,p) (of small variance) were (essentially) confined within one resolver level, then only a single reading would occur with high probability. The variance estimate would then be (nearly) zero, However, moving the mean would shift the distribution into various. levels, and at least some data would seemingly be meaningful after mean-shift sub- traction and other processing. The effects of mean-shift by various deterministic func- tions is difficult to determine analytically because the P(0) integral is transcendental. However, these effects can be readily modeled for machine computation, and this approach prevails in the remainder of the discussion. Ill. Resolver Error Model Function and Mean-Sweep Variance is estimated from data as the mean-square value of the data set, all data as deviations from the average value. During data collection, probabilities are not normally tabulated; they simply "occur" as variations in the number of data samples in the various class inter- vals. For finite data, the number of class intervals ob- tained is directly proportional to the resolution of the data samples with respect to the standard deviation. Phase samples from the DSN doppler counter occur in class intervals Ap wide, all samples in the class interval yielding the sanic value, K10, where K is the index of the interval. For example, in Fig. 1, without differencing, the rel,_ tive contribution of the shaded area (A,) to the variance estimate would be (assuming an infinite sample popula- tion with = 0, and neglecting mean offset of the area) U 2 (A ,) ` (4A0)2J 05 P(¢) d p 4Aq5 + So,, = (A!! (6) while the trice contribution is 4S ff (As) = Joy o^ P(o)do (7) Equations (G) and (7) show the essential error source; errors occur because, with sample data, a single value is used to represent the mean-square data of an entire region, the group interval_ The true variance is defined such : that the data are continuous and . samples are "inside" the integral, squared for integration %vith the corresponding probability density coordinate. There is obviously some value of phase that could be subtracted from 4AO of (6) (Bolding A, constant) for equivalence with (7); such values, however, would not be static, but would rather depend on Cp l,. The "correction" is thus 11011- static and must be determined as a function of the areas, or, finally, of die variance estimate. It is intuitive that the variance error will increase when the probabilit y integral is large with respect to variance. When the limits are infinite, this integral is unity', and the entire estimate is a single measure, which is mean- ingless. On the other hand, when the interval is (relatively) small with respect to variance, the estimate and true values asymtotically approach, for the relative change in argument across each interval is small. If mean-sweep is introduced, the class interval associ- ated +with a given estimate, such as 4A0, shifts in location, while the actual estimated angle (& — ^) takes on a variety of values. A "weighted average" contribution to variance thus occurs for each O K = KAcA — Sp. The model for this estimate and its true counterpart can be expressed in some detail by (including a nonzero initial mean) o(t)] do dt '( — (Af'V)` 111 Y JJJ ^i 1^) J tfx n ,-_x ¢n f^f1.ap fn-4aej l "P(^ 14] dt } J) — (AIN)-- (9) T RIO) do ^ :, x--n L ¢h - 4tsrrj (10) ap = phase noise variance crp estimate of ao during typical measure- ment cp =. phase . noise deviation from mean. (con- tinuous variable) P(¢) = probability density function of °argu mc:nt; commonly "normal" or "gaussian" 166 JPL DEEP SPACE NEIVORK PROGRESS REPORT 42-25 K = index of resolver phase levels modulo ?' OK = expression of resolver levels as incre- J u - t h h '' N " 41, mental phase deviations, A¢ wide, from 0<„ the phase level nearest the nominal ¢h. _ ¢f irti .3Q ¢h Q,arTi . 5¢ P(02,) dq,_ X J P(4,:) d¢, 40mean h -¢fdlr ¢h -¢,Lt-t, AO = O N increment, 3.6 deg (1.0 \4Hz) or 18 (IIN)- (12) —deg (5.0 MHz) 2 11I N = P(0) mean value, exclusive of ¢ where r = sample interval, usually 1,0 or 0.1 s T =total measurement period, i0 s to sev- AM = intentional change: in mean please during eral minutes sample period — KL, KL = lower and upper index limits for class two arbitrary sequential phase measures, intervals of obtained data taken T seconds apart Tt), (cite) = deviations of mean value of 0 distribu- tion, at time t, from nominal value. At Note that the bias mean offset from o,,, 50,,, contained times At-r, the nominal (null) value is in all OK , is not normally known, so any mean-sweep the modulo B- bias waveform phase function will necessarily have an arbitrary zero reference, within the resolver; 0„ + SO,, = 0; ¢(t), whose affect may or may not be finally significant. Also, (llT) are presumed intentional and if P(¢) is a stationary function about the mean, 3tN will known be zero upon differencing, and may be dropped. Note: that (9) differs from (10) in that (10) is not only The factor `" " in eachexpression results because thediscrete in the mean-sweep function, but alga the phase diffvrenced distribution variance is automatically twice measures¢ — ^(AIT)} are again outside a£ the proba-Ke( as large as the variance of the primary distribution. Thisbilitj• integral. Each set of measures therefore represents, is well established once will not be covered here.as before, a class interval of probability given by the class interval integral. Conversely, (9) is exact, since ¢= is within the integral. Note that, in (10), many more class intervals are ob- tained because the mean-sweep functions is not constant, but steps to various values. These intervals are not dis- tinct but overlap; the error is not "removed," but rather "pseudo-averaged" to some difference value by sweeping. Various undesirable effects mentioned earlier, but not evident in (10), lead to actual data reduction as a differ- encing of the sequential (KAO) obtained. Upon differenc- ing, .the. defining expressions become somewhat intricate multiple sums and integrals, For actual. machine programming, P(,p) was considered gaussian and therefore stationary, The error-function sub- routine, adjusted for gaussian form, was used to evaluate the integrals. Also, (11) could feasibly be expressed as a single integral since the difference between variates in a gaussian distribution is itself a gaussian distribution tvitb doubled variance. Sweep is obviously irrelevant since it would simply "subtract out" as an additive -contribution. However, to avoid undue complication, (12) is easier to handle: in the double-intcgraI form, since mean-differences cause probability changes between samples. The single- integral form was modeled, but it was more complicated than .(11), so it was dropped ,in favor of the expression as stated. X P (O, -; ( t + -)) P LOD - ^(t)] do,dp dt^— (lI ')= {Zl) Data on available DSN hardware indicated that sinu- soidal modulation index could be set within a tolerance of —_5%. 'With this in mind, a simulation program for (12) was automated. The program routine to calculate esti- mated sigma was: JPL DEEP SPACE NETWORK. PROGRESS REPORT 4225 167 1 l r.-^ xr, sf Q "—(N-%0)'-'[erf (6_) -- erf (B,)I X [erf (0,) — erf (B:,)I — 9T [en1(lrr)I=^ Bt _ [K 0 — r ( Zlr — r) — S,ha l VJ^'o B_ = B t -'- Ao/^ffv¢ [(K + N) A¢ - ^(Alr) ..... 90IB:. _ 11 I- Kz W int + 1 0 (no sweep) x(,11 r.) _ (,11r/T) A-^ (lin car sweep) ¢,r sin [2,r lf-/TI (sinusoidal sweep) 0 (no sweep) A.Ig lir) = (r/T) A0 (linear sweep; no appreciable error) & ( sin [2= Mr/T] — sin [27r (11- — T)/TI) ¢,^ = estimated modulation index, deg ^„ = true modulation index, deg 80,> = initial offset, 0 C S(¢„ C A0 (13) Note that o,,, the true (but to known) modulation. index, appears in the error function .integral, while 0^,f, the data reduction value, appears only in the rrns correction due to sinusoidal sweep. , Since the resolver mean offset S¢„ is modulo A-h, it is evident that limiting S¢„ to a spread of A0 will cover all variation. Au initial investigation with machine programming of (13) alone indicated that the error variation with modulation index sp,f tended to in- crease when 0,1 was greater than A0 or less than about AO/3. Therefore, detailed investigation was Iimited to this range. Results used had the tolerance spread M = Yor ov - oif, 0!r 4 5 . ^hu - 5% n = 4 for So„ = 0, 0.9, 1.8, 17 (I5) where B„ the mean error, or average- offset, between given sigma and its estimates e' , y (6p} — the rms value of thca variation in Q¢ for given uo due to (uncontrollable) tolerances in 011 and initial values of Soo. The error statistic e,,,„ is not a random variate but is bounded b_v the tolerance excursions and their combined effects. Equations (14) and (15) complete the quantitative description of the model program. The program inputs were sigma (,T,,), sample interval (r), sweep repetition period (T), and estimated modulation index (pm), The fundamental sweep frequency was obviously VT Hz, To avoid the region where autocorrelation effects would possibly occur in practice, r %vas chosen as 1.0 s. The period T %vas then set arbitrarily at 10.0 s. This yields the lowest practical sinusoidal sweep frequency (0.1 Hz) available at the DSN sites. A lower frequency would yield a higher sweep resolution, obviously desirable,. but not presently feasible. Sigma values from 0.4 to 3.0 deg were processed as the modulation index was varied over the stated range. Also, highly resolved linear sweep (-.IT 0.01) as well as no- sweep conditions were cycled, and the various data were collected for analysis, IV. Mean-Sweep Effects and Error Analysis An error measure was also in the .program along with a mean error (offset) calculation. These measures were 1 in n ,i, 4 1 `' r,ns t4) — rn rr Po ( .uQ, so-'6) — 0. (Qp)]z (14) At the other extreme, the error with -no-sweep was lIn (13), this correction has been separated from the main art;t,- larger than o-, itself at the lower values (below 0,5 or ment for independent evahtation. This is possible upon difierencing; 2.5 deg) and rendered the measure questionable until u¢ the cross-correlation is zero: was greater than 2,0 deg (or 10 deg)_ Foe sigma greater !68 JPL DEEP SPACE NETWORK PROGRESS REPORT 42.25 The error statistic e'= „ represents a medium value of the variation in the estfrnate of the error, as to be ex- pected when measuring doppler phase-noise sigma while sweeping. With the highly resolved linear . sweep, this error -,vas all but undetectable. Such sweep would be preferable to all other forms, except that it is difficult to mechanize during coherent testing. than Oiese levels, sweep made little difference; the error was of gligible. Wi th sinusoidal sweep, the error in the region of inter- est was less than once-fourth the no-sweep level for all modulation indices programmed. Within this bound, how- ever, the relative error was vary sensitive to the actual bar. Tho p;; between 1 and 3 deg was tried, and the opti- mum value appears to be about 1.5 deg. The error dis- tribution with various Oar was very erratic within these small limits, but finally insignificant because of their low absolute level. Within the measurable range, the erns error never exceeded 0.15 deg (1.0 \[Hz) while sweeping (co -- 0.4 deg), and this model level, in practice, will undoubtedly be masked by other system contributions. In order to facilitate easy mechanization, a.modulation index of 2.0 deg was selected for test use, as compatible with the DSN Command X-lodulator Assembly (CMA:) equipment. A typical sinusoidal-sweep error distribution. of rrp, yielding E°,,,,, and Q,,, is show,: in Fig. 2 as a function of Boo and , . The figure, for a ups of 0.6 deg, clearly shows the pseudo-sinusoidal nature of the error; peak error is less than 1.5 times the rips value. Composite error results . described above are shower in Fig. 3. Note the large error reduction in the small-sigma range by sinusoidal sweeping as opposed to the existing no-sweep condition. Also note the convergence of all data at about 2 deg (or 10 deg); sweeping to improve statistics above these levels is, as noted, superfluous. For Aq5 — 3.6 deg (1.0 MHz), this is 1.039 deg, in excel- lent agreement with the data. Since the variation in 40 with (ro is so small, the easiest correction to data is to simply subtract the B,, limit as an rms level: n n n., ^^s ^Q r.,irrecird pc ^V" — 12 (17) This is the expression recommended for DSN doppler noise: correction (with or without sweep) to account for the finite resolver group interval error, as desired. . The final distribution of..^, with (17) and sinusoidal sweep with ¢,r = 2 deg alapiie d (one-signia error limits) for no sweep is shown in Fig. 4; ^p (corrected) is the expected range of values during DSN data reduction when-the specified sweep. is used. V. Conciusions The primary purpose of doppler phase-noise measure- merit is to estimate the noise content of the doppler data obtained operationally and to assure that this noise is within specified bounds. This discussion has concentrated on the low-noise. cases. Operational data occurs with natural mean-sweep, often nearly linear, as a result of relative ground— spacecraft motion. Tasting without sweep thus cannot accurately predict the operational noise in the strong- signal region; the estimate (as analyzed here) will nor- mally be too variable. The statistic B„ in (14) is very interesting.. For ^u of deg, the selected value B„ varies from an asymptote of about 1.040 deg (1.0 \-1 Hz) at the higher levels of ao down to 1.023 deg at the minimum measurable level, an insig- nificant change of only 0.017 clef; across the entire. field. It obviously differs little from a constant rms offset, apparently related to the resolver increment Ach. With .a little manipulation, the limiting. value of this offset can he shown to have a well-known quantization error value (omitting intermediate steps): .. x 1IIi-til ail lim (Bo) = = Iim I AL--^A6 ¢ P(O;U) do — Er" Q-.x a-^-= hLL-x ^ I In the S-band region (1.0-\i11z bites) the no-sweep error is small except for somewhat unusual conditions; normally without operational application. Low-noise occurs, for example, when testing under full' coherent conditions; resulting in.. cancellation of exciter noise within the dop- pler extractor, However, -when. such conditions are e:n- countertd, as during trouble-shooting, mean-sweep will improve , the residual measure (of the receiver) by reduc- ing. advc se resolver effects. Such effects have been encountered iii practice. In the X-band region (5.0-\1Hz bias), system noise is comparable to or less than resolver error without sweep. Measure of system noise, as it occurs operationally, ap- pears to require it correction such as that of the sweep J^ technique, It will remove a significant variability present 12 (16) during test, but normally absent during active tracking. i { Sweep with the stated parameters reduces the rms of the test error by as much as 4-to-1 in the applicable region. Independent of sweep effects, there exists a resolver quantization offset error, unavoidable because of the in- cremental pulse: spacing. This will be present on all data, operational and test, and is about I deg at S-band (1.0 MI-1z) or 5 deg at 1-band (5.0 MHz). If system noise or operational. data outside of counter effects are to be measured, this offset must be removed. However, if an operational noise estimate is to be made, this may or may not be included as appropriate. For testing without this effect, it is recommended that the offset be extracted from the calculated estimate of counter input noise. To summarize, when the bias is fixed and coherent, a sinusoidal sweep (by exciter phase modulation), with amplitude ? deg and frequency 0.1. Hz, will adequately simulate natural operational sweet. This will reduce counter error sufficiently that m ,,a.,`:jgful results at sigma levels below ? deg (1 M11z) zwd I (5 X111z) can be obtained. An additional fixed resolver quantization error of 1.039 deg (S-band) or 5.19 deg (X-band) ma y be sub- tracted (variance subtraction) as desired; it is it "built in" error on all doppler counter measures, Definition of Symbols (all time notation in seconds; all phase notation in cycles or degrees) AK Kth area of probability density function between resolver levels a index (subscript) for modulation index B bias frequency, 1.0 to 5.0 MHz b index (subscript) for initial mean offset angle S¢a E",,,,, root-mean-square error of given sigma measure K resolver level index, resolver level pease sub- script & nominal K nearest (below) bias-mean zero- crossing KL summation limit for K (absolute) M discrete measurement index and subscript ra summation limit, modulation index N differential K on successive measures n summation limit, initial. offset phase P(.A) probability density function notation t time, general notation, s tp time of measurement pulse t_ time of first positive-going zero-crossing after t„ T total measurement period;. period of periodic sweep aT actual time from tp to k. in resolver 4To mean value of AT, due to bias alone. AT resolver time increment, 10 ns Air resolver phase increment BA7 = 3.6 deg (1.0 MHz), 18 deg (5.0 NlHz) ALAI change in ^ between successive measures ST resolver time error in measurement of AT ST, mean value of ST, due to bias alone So resolver phase error in measurement of Ole S¢o mean value of S-p, due to bias alone phase-noise displacement, general Ox resolver Ievel phase notation set 0, total residual phase displacement from bias mean KA¢, the resolver estimate of ¢rc Ou phase modulation index during sinusoidal sweep far operational estimate of $u intentional mean displacement of P(0) from bias mean; sweep function value B„ mean value of tins error between vQ and vp, given v4 r sampling interval, nomina lly 1 s ap sigma (standard deviation) of q, TO estimate of crp using counter data corrected value of 0, based on a., 170 JPL DEEP SPACE NETWORK PROGRESS REPORT 42-2-5 Fig. 1. Doppler counter resolver timelphase relationships (S) 0 1 2 3(X) 0 5 10 15 Q¢, deg 1.5 1.4 1,3 Fig, 3. Phase -noise measurement error as a function of sinusoidat mean -sweep for various modulation indices !x) (s) i 15 3 "' i T = 1.05 T=10.0s 'CORRECTED ^t/2 Ca - (1.039) 2 3 10 2 j rn +E, NO SWEEP A O cb^ 5 1 MIS ^// l.^-cam, NO SWEEP 0 1. 2 3 A¢ 0. D 80o, deg (X) a 5 0 I5 deg Fig. 2. Typical variation in noise sigma estimate v° as a func- tian of resolver mean offset o„ and modulation index tolerance Fig. c}; Corrected sigma estimate vs sigma: no-sweep and ^^ -E 5%; a = 0.6 deg sinusoidal sweep (mod 'index 2°) JPL DEEP SPACE NETWORK PROGRESS REPORT 42 .26 yy 4" 171 1.2 6 1.t v cb 1,0 0.9 0.e 0.7 .: (60} 0.6 ^ k i j 1 k I k K4¢ = = 44O (X) (s) SHIFTER 5,0 K = 4 INDEX: PHASE MODEL OF K K0 = 0 COUNTER/RESOLVER ( WITH MEAN-SWEEP) 8^p S¢p A4 1 I OR 0-2 0-1 "0 i't 02 03 04 05 "6 RESOLVER LEVE^ TYPICAL (0 )K TIME BEHAVIOR I i 71 OF COUNTER/RESOLVER NOMINAL 1 R 2.5 I ZERO-CROSSING I ZERO-CROSSINGI I i ^ I I °W COUNTER I RESOLVER I I r K-I K l r K Dr (K - K )4r' K = RESOLVER0 0 READOUT ATO !K - Ka 4r ( BEFORE ST INDEX SHIFT) K^r 1 -- DT t rz 0 1.0 0,9 0s 0.7 OM = 0° (NO SWEEP) 0.6 0.5 0.4 0,3 ^!A = 2', 10° 0.2 0.1 D r 4 i Bibliography Anderson, J. D., Null, G. W., and Thornton, C. 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