Instrument data systems consist of a microprocessor, 3K bytes of Read Only Memory and 3K bytes of Random Access Memory. It interfaces with the spacecraft data bus through an isolated user interface with a direct memory access bus adaptor, and/or parallel data from instrument devices such as registers, buffers, analog to digital converters, multiplexers, and solid state sensors. These data systems support the spacecraft hardware and software communication protocol, decode and process instrument commands, generate continuous instrument operating modes, control the instrument mechanisms, acquire, process, format, and output instrument science data

Barry, R. C.

English

NASA Technical Reports Server

EIGHT MICROPROCESSOR-BASED INSTRUMENT DATA SYSTEMS IN THE
GALILEO ORBITER SPACECRAFT*
Robert C. Barry
Jet Propulsion Laboratory
Pasadena, California
The Galileo Orbiter spacecraft carries nine scientific instruments,
all but one of which are controlled by individual microprocessors. Scientific
investigations include interplanetary measurements of charged atomic particles,
magnetic and electric fields, and dust. In orbit, Galileo will investigate
Jupiter's magnetosphere and atmosphere; and surface properties of the four
largest satellites. Launch is scheduled for early in 1984.
While the. complexity of the instruments and their data systems varies widely,
all utilize components from the RCA 1800 microprocessor family, and all perform
the same basic functions. The decisions to utilize microprocessors in the
instruments were heavily influenced by the spacecraft distributed Command and
Data System (CDS) design which uses this same LSI family.
A typical instrument data system consists of a microprocessor, 3K Bytes of
Read Only Memory (ROM) and 3K Bytes of Random Access Memory (RAM). It interfaces
with the spacecraft data bus through an isolated user interface with a direct
memory access bus adapter. Microprocessor control and data lines provide
interrupts, serial, and/or parallel data from instrument devices such as registers,
buffers, analog to digital converters, multiplexers, and solid state sensors.
These data systems support the spacecraft hardware and software communication
protocol, decode and process instrument commands, generate continuous instrument
operating modes, control the instrument mechanisms, acquire, process, format,
and output instrument science data.
The approach has resulted in many specific improvements over past missions.
Some of the most important include: increased instrument autonomy, functional
commanding, and macro mode generation; enhanced telemetry output from both
operational and scientific points-of-view; and additional flexibility for in-
flight optimization, problem work-arounds, and instrument generalization for
support of multiple missions.
There was a significant but manageable underscoping of the microprocessor
development tasks and costs. This was related to difficulty in establishing
firm requirements at an early date, interfacing complexity, parts acquisition
problems, and a general lack of extensive experience in microprocessor hardware
and software design. .
While the Galileo entry-level introduction into instrument microprocessor
appears to be proceeding well, additional effort is needed for standard use of
microprocessors in science instruments to achieve a significant part of its high
potential benefit. This includes generation and clarification of spacecraft system
level requirements in concert with the objectives of the end-to-end information
system design, improved use of microprocessor development tools and practices,
and justification for increased instrument funding compatible with the increase
in capability and cost.
*This work was performed for the Jet Propulsion. Laboratory, California Institute of
Technology, sponsored by the National Aeronautics and Space Administration under
Contract No. NAS7-100.
https://ntrs.nasa.gov/search.jsp?R=19810003138 2020-03-21T16:10:40+00:00Z
O
INTRODUCTION
• HISTORICAL ASPECTS OF INSTRUMENTS ON JPL SPACECRAFT
• INCREASING COMPLEXITY
• HIGHLY INTEGRATED SPACECRAFT
• HIGHLY INTEGRATED MISSION OPERATIONS & FLIGHT TEAM
• EXTENSIVE DATA PROCESSING & CORRELATION THE NORM
• WHAT ROLE DO INSTRUMENT MICROPROCESSORS PLAY IN THIS?
• NOT A DRAMATIC CHANGE, A NATURAL EVOLUTION
• VERY FLEXIBLE, EXPANDABLE CONCEPT
• GALILEO IS THE STARTING POINT
• LIMITATIONS OF THIS PRESENTATION
• RESTRICTED TO A HIGH-LEVEL, BRIEF REVIEW
0 TIME RESTRICTIONS FORCE GENERALIZATION
• ACCENTUATE COMMON ELEMENTS
• LITTLE DISCUSSION OF UNIQUE IMPLEMENTATIONS
MATERIAL TO BE COVERED
• REASONS FOR USE OF MICROPROCESSOR-BASED DATA SYSTEMS IN THE INSTRUMENTS
• FUNCTIONS PERFORMED BY THE uPs
• SUMMARY OF THE INSTRUMENTS
• SELECTED HIGHLIGHTS FROM THE GALILEO APPLICATIONS
• PROBLEM AREAS ENCOUNTERED
• EVALUATION OF THE GALILEO APPROACH
WHY USE MICROPROCESSORS IN THE GALILEO INSTRUMENTS?
• SUPPORT THE GENERALIZED SPACECRAFT SYSTEM INTERFACE (BUS)
• PROVIDE INCREASED INSTRUMENT AUTONOMY
t REDUCE REQUIREMENT FOR SPACECRAFT SERVICES
• INCREASE INSTRUMENT DESIGN CONTROL
• UTILIZE SEMICONDUCTOR INDUSTRY ADVANCES
• AVAILABLE/ PROVEN LSI PRODUCTS (RCA CDP1800 SERIES)
• DECREASE POWER AND MASS REQUIREMENTS (CMOS LSI)
• INCREASERELIABILITY (REDUCE PARTS COUNT)
• SIMPLIFY DESIGN (REPLACE DISCRETE, MSI LOGIC)
• EXTEND INSTRUMENT CAPABILITY (FALLOUT, NOT A REQUIREMENT)
• ADD FLEXIBILITY TO ACCOMODATE CHANGING REQUIREMENTS (SOFTWARE)
t PROVIDE ENHANCED MODE GENERATION AND CONTROL (MINIMAL H/W)
• GENERALIZE INSTRUMENT
0 MODIFY OR UPGRADE FOR FUTURE USE ON OTHER SPACECRAFT
INSTRUMENT DATA SYSTEM FUNCTIONS
• SUPPORT SPACECRAFT INTERCOMMUNICATION BUS AND PROTOCOL
0 DECODE AND PROCESS INSTRUMENT COMMANDS
0 GENERATE INSTRUMENT OPERATING MODES
0 CONTROL MECHANISMS .
0 PROCESS SCIENCE DATA FOR OUTPUT
DATA SYSTEM FUNCTIONS
• SUPPORT OF SPACECRAFT BUS AND PROTOCOL
• SERIAL, SYNCHRONOUS DATA AT 403.2 KBPS
t ISOLATED USER INTERFACES (TRANSFORMERS)
• MEMORY TO MEMORY TRANSFER USING DIRECT MEMORY ACCESS
t S/C COMMAND DATA SYSTEM (CDS) INITIATES. AND CONTROLS ALL ACTIVITY ON A TIME
MULTIPLEXED BASIS .
t DECODING AND PROCESSING OF INSTRUMENT COMMANDS
0 ACCOMODATE VARIOUS INPUT DATA
0 COMMANDS
• MEMORY LOAD
• S/C TIME AND SPIN DATA
• PROCESS COMMANDS : . . .
0 ERROR CHECKING & VALIDATION
0 UPDATE OF INSTRUMENT STATE.DATA
DATA SYSTEM FUNCTIONS (CONT'D)
0 GENERATION OF INSTRUMENT. OPERATIONAL MODES
0 ALLOW FUNCTIONAL LEVEL COMMANDING (TYPICALLY 3 TO 8 MAJOR MODES)
0 REDUCE INTER-SUBSYSTEM COMMUNICATION
0 SYNCHRONIZE. WITH SPACECRAFT TIMING•
0 PROVIDE MORE MODE GENERATION FLEXIBILITY TO THE INSTRUMENT •
0 MECHANISMS CONTROL FUNCTIONS (SENSORS, FILTER WHEELS, MULTIPLEXERS, ETC.)
0 SENSE MECHANISM STATUS
0 GENERATE CONTROL SIGNALS
0 ACQUIRE AND BUFFER DATA .
0 SCIENCE DATA PROCESSING
0 APPLY ALGORITHMS TO PROCESS DATA (COMPRESSION, STATISTICS, DE-SPIN, ETC.)
0 FORMAT DATA (CONTROL SUBCOMMUTATION, ADD ENGR &.STATUS/ETC.)
0 OUTPUT TO BUS UPON REQUEST
11
INSTRUMENT SUMMARY
ABBR.
SSI SOLID STATE IMAGING
NIMS NEAR INFRARED MAPPING
SPECTROMETER
PPR PHOTOPOLARIMETER
RADIOMETER
UVS ULTRAVIOLET SPECTROMETER
EPD ENERGETIC PARTICLE DETECTOR
PLS , PLASMA SUBSYSTEM . .'
MAG MAGNETOMETER
DBS DUST DETECTOR SUBSYSTEM
PWS PLASMA WAVE SUBSYSTEM
(NO nP) '
PRINCIPAL INVESTIGATOR
DR. J.S. BELTON,
(TEAM LEADER)
DR. R. CARLTON,
(TEAM LEADER)
DR. J.E. HANSEN
DR. C.W. HORD
DR. D.J. WILLIAMS
DR. L.A. FRANK
DR. M. KIVELSON
DR. EBERHARD GRUN
DR. D.A. GURNETT
INSTITUTION
KIT PEAK NATIONAL OBSERVATORY,
TUSCON, AZ
JET PROPULSION LABORATORY, ,
PASADENA, CA
GODDARD INSTITUTE FOR SPACE STUDIES,
NEW YORK, NY
LABORATORY FOR ATMOSPHERIC AND SPACE
PHYSICS, BOULDER, CO
NOAA SPACE ENVIRONMENT LABORATORY,
BOULDER, CO
1
UNIVERSITY OF IOWA,
IOWA CITY, IOWA
UCLA
LOS ANGELES, CA
MAX PLANCK INSTITUT FUR KERNPHYSIC,
HEIDELBURG, WEST GERMANY
UNIVERSITY OF IOWA,
IOWA CITY, IOWA
INSTRUMENT COMPLEXITY COMPARISON
NO
1NST
SSl'
NIMS
PPR
UVS
EPD-1
EPD-2
PLS-1
PLS-2
DDS
PWS
ROM
KBYTE
3
3
4
—
,4
2 .
4
(SAME
3
—
RAM
KBYTE
3.5
1.75
0.25
0.75
2.66
0.25
4
AS PLS-1)
2
0.25
TELM DATA
(KBPS)
768. TO 0.02-
11.52
0.18
1.0
0.92
— -
0.6
.024
645.. TO 0.2
DATA
MODES
3
6
5
3
15
—
7
3
2
COMMAND
PARMS.
24
31
12
20
150
50
110
33
•7
NO . NO
MECHANISMS SENSORS
9 800 x 800 CCD
9
10
6
50
3
31
9
11
17
3
3
17
-
20
4
3
MASS
(KG)
28.0
18,1
4.3
4.2
8.5
(INCL
10.7.
4.0
5.3
PWR
(WATT)
25.
16.
12.
4.5
8,6
ABOVE)
9.5
1.8
5.6
(NO
12
INSTRUMENT DATA SYSTEM HIGHLIGHTS
(SELECTED PROP! AMONG THE EIGHT INSTRUMENTS)
1) FUNCTIONAL COMMANDING AND MACRO MODE GENERATION
2) TASK ALLOCATION BETWEEN MICROPROCESSOR AND OTHER INSTRUMENT HARDWARE
• HIGH RATE DATA TRANSMISSION
• SPECIALIZED PROCESSORS (FORMATTERS, MULTIPLIER, ENCODER/COMPRESSOR, ETC.)
e SOFTWARE OVERALL CONTROL
• HYBRID INSTRUMENT OPERATION (WITH OR WITHOUT uP)
3) ENHANCED DATA ACQUISITION & TELEMETRY OUTPUT
• SUBSYSTEM UNIFORMITY
• ADDED ENGINEERING VISIBILITY (SPECIAL HIGH-RATE MODES, SUBCOI1S, ETC.)
• SOME ADDITIONAL ON-BOARD PROCESSING & BUFFERING (DATA DISCRIMINATION, DATA SEARCH,
OPTIMUM AVERAGING, COMPRESSION, ETC.)
4) MEMORY RE-ALLOCATIG'I AND REPROGRAMMABILITY FOR SCIENCE MODE OPTIMIZATION AND RESPONSE
TO SUBSYSTEM OR SPACECRAFT FAILURES
• RAM MARGIN
• RAM REPLACEMENT OF ROM VIA BUS COMMAND
• ROM LINKAGES TO RAM FOR SUBROUTINE REPLACEMENT
INSTRUMENT DATA SYSTEM HIGHLIGHTS (CONT'D)
5) HIGHLY FLEXIBLE APPROACH
• ALLOWS SUBSYSTEM OPTIMIZATION
• WIDE RANGE OF DATA RATES
• 8 UNIQUE DESIGNS
6) CLEAR BENEFIT IN LOGIC REPLACEMENT OBSERVED
.7) ADVANCED DATA SYSTEM TECHNIQUES
• MULTIPLE MICROPROCESSORS
• POWER HSARING, FAILURE ISOLATION
i AUTO-CALIBRATION
• BACKGROUND PROCESSING, HIGH LEVEL LANGUAGE (FORTH)
8) COMPATABLE WITH LONG-RANGE DEEP SPACE EXPLORATION DESIGNS AND GOALS
• PACKET TELEMETRY
i ADDED AUTONOMY
t-EEIS
13
PROBLEM AREAS ENCOUNTERED .
1) HARDWARE DESIGN LIMITATIONS AND CONSTRAINTS
• SPACECRAFT MASS, POWER, AND RELIABILITY REQUIREMENTS
• LIMITED OPTIONS IN uP AND CHIP FAMILY SELECTION (1802, 1852, 1856, 1834,
TC244)
• LIMITED MEMORY SIZE (RAM IS 256 x 4 BITS)
• JUPITER MISSION REQUIRED HIGH RADIATION TOLERANCE '
• PARTS DEVELOPMENT AND ACQUISITION PROBLEMS .
• CAUSED INCREASED COST, SCHEDULE PROBLEMS
2) USE OF READ ONLY MEMORY (ROM) AS PRIMARY PROGRAM MEMORY
• INCREASED COSTS AND SCHEDULING PROBLEMS
• DECREASED FLEXIBILITY
• INCREASED NEED FOR EARLY SYSTEM-LEVEL VALIDATION
3) UNDERSCOPING OF MICROPROCESSOR DEVELOPMENT TASKS AND COSTS
• SOFTWARE, SOFTWARE MANAGEMENT AND DOCUMENTATION
• DEVELOPMENT SYSTEMS AND SUPPORT EQUIPMENT
• INTERFACE REQUIREMENTS STABILITY
• ADDED TESTING COMPLEXITY
PROBLEM AREAS ENCOUNTERED (CONT'D)
4) BUS DESIGN
• BUS ADAPTER COMPLEXITY
• LOW ERROR REQUIREMENT
• OPEN-LOOP PROTOCOL (NO HANDSHAKE)
5) SYSTEM LEVEL REQUIREMENT IMMATURITY
• END-TO-END INFORMATION SYSTEM (EEIS) GOALS REDUCED
t EARLY INTERFACE REQUIREMENT STABILITY AND DETAILED DESCRIPTION
6) PERSONNEL EXPERIENCE AND TRAINING
• vP . . .
• SOFTWARE
14
EVALUATION OF THE GALILEO APPROACH
>
• CURRENT STATUS
0 MOST INSTRUMENTS HAVE AN OPERATIONAL BREADBOARD DATA SYSTEM NOW
• EXPECT ON-TIME DELIVERY OF ADVERTISED CAPABILITY
• EXPECT TO SIGNIFICANTLY ENHANCE THE SCIENCE VALUE OF THE MISSION
• EACH INSTRUMENT PROVIDES SCIENCE OPTIMIZATION FOR ITS INVESTIGATORS
t EACH HAS PROVIDED FOR INCREASED IN-FLIGHT FLEXIBILITY
• ADDITIONAL EFFORT MUST BE EXPENDED TO SOLVE PROBLEMS ASSOCIATED WITH:
. • SYSTEM REQUIREMENTS DEFINITION
t IMPROVED USE OF MICROPROCESSOR DEVELOPMENT TOOLS
• FUNDING CONSISTENT WITH THE ENHANCED CAPABILITY AND COST
FUTURE PROJECTIONS
• TECHNOLOGY IMPROVEMENT
• SEMICONDUCTOR TECHNOLOGY (ADVANCED wP, DENSE MEMORY, HIGHER SPPED, ETC.)
• ADVANCED ARCHITECTURE AND SOFTWARE DESIGN (MULTIPLE MICROPROCESSORS,
HIGH LEVEL LANGUAGES, ETC.)
• APPLICATION ADVANCES
0 INSTRUMENT AUTONOMY
• HIGHLY FUNCTIONAL COMMANDING
0 -EXTENSIVE ON-BOARD PROCESSING (ESPECIALLY FRONT-END APPLICATIONS)
15


Eight microprocessor-based instrument data systems in the Galileo Orbiter spacecraft

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