The TRAK Systems' GOES Satellite Synchronized Time Code Generator is described. TRAK Systems has developed this timing instrument to supply improved accuracy over most existing GOES receiver clocks. A classical time code generator is integrated with a GOES receiver

Fossler, D. E.

Olson, R. K.

English

NASA Technical Reports Server

NEW GOES SATELLITE 
SYNCHRONIZED TIME CCDE GSNERATOT4 
D. Earl Fossler and Roger I : .  Olson 
TRAK Systems, a Division of TRAX Microwave Corp. 
Tampa, Florida 
ABSTRACT 
This paper describes the TRAK Systems' GOES Satefiite 
Synchronized Time Code Generator. T94Y % = f e ~ ~  h=.= 
developed this timing instrument to supply improved 
accuracy over most existing GCZS receiver clocks. 
Integrating a classical time code generator with a 
GOES receiver combining the best of both. 
IWTRODUCTION 
During the last few years, several. GOES Satellitie Time 
Receivers have been designed by various manufacturers. All 
output time with accaracies of 2 milliseconCs or better (at 
least one has a reported accuracy of better than 1QO 
microsrconds) when locked to the satellite signal but all lack 
several features desired by many users. All known designs 
cannot output a usable time signal between power turn-on and 
signal acquisition. When synchronizatio~ with the satellite 
signal is lost, the accuracy of the time outputs degrades 
rapidly in many designs. The 1P?S output in several designs 
exhibits significant jitter during various microproces+or 
activities. Output options are very limited and speciai 
outputs are cot economical, 
There has been a significant interest to correct these 
deficiencies by providing a manually presettabie time code 
generator which can operate as a stand alone generator or 
fully synchronized to the satellite signal. Until now this 
could only be accomplished by purchasing two separate units 
from two suppliers. As r result of these problems, TRAK has 
designed a new timing instrument to correct these deficiencies 
in a single timing unit. 
https://ntrs.nasa.gov/search.jsp?R=19850020935 2020-03-22T19:43:03+00:00Z
PRODUCT DESCRIPTION 
TRAK Systems Model 8600 Satellite Synchronized Generator is a 
precision time oignal generator with an internal CCES 
satellite rsceiver used Lo synchrcaize the generator. The 
single 1-3/4-inch high r a w  mounca3le inst,ru~ent provides for 
both a satellite synchronized timo signal aenerator or a 
manual front panel settable time signal generator. 
This Synchronized Qeneratnr was designed to provide an 
accurate time source when synchronized to t,he GOES Satell~te. 
It also will function as a local time source ~ h e c  
synchronization is impossible. 
This unit generates time by counting down either an external 1 
MHz input or using its internal temperature controlled oven 
crystal oscillator. W h e ~  syschroniz~d to the satellite 
slgnai, tl-,c5e count down registers are continuously 
synchronized to the satellite 100 Hz reference. In this mode, 
the time cf day accumulator will be set and periodically 
upd~ted sing the satellite data. Initial setting may also be 
done manually to sroqide usable time outputs before the 
satellite data is acquired. 
The only required set-up mode parameters are Latitude and 
Longitude of the receiver site. These val~es are inputted via 
the front panel switches and stored in a non-volatile RAM. 
Time zoae offset may also be entered to dllplay and output 
local time. 
The UHF receiver is a completely shielded coherent synchronous 
digital dual converc'on receiver with automatic tuning for 
reception of both t h e  GOES East and GOES West satellites. The 
receiver is fully enclosed ir a metal case and located wi~hin 
the generator chassis. Signal enhancement and data detection 
is accomplished outside the receiver. Data and clock are 
inputted to the microprocessor for frame synchronization and 
data processing. 
A microprocessor is used to control various operations of the 
unit. It is used to examine the detected satellite data, 
provide frame synchronization, test data for bit errors, 
selest good data, calculate path delays, correct data for 
actual path delay, synchronize clocking freq~~ency to the 
satellite clock, provide for synchronous time update and 
provide for interface with R S 2 3 2  and IELE 488. 
Path delay calculationr are performed on initial acquisition 
and each time a change of satellite position is observed. The 
signal path delay is calculated with a resolution of one 
microsecond and with an accuracy of better than 10 
microeeconds. 
Tho time of year accumulator, its minor scaler (fxequency 
divieers), the parallel time outputs and the serial time code 
generator(r) are a11 hardware to provide macinum time signal 
accuracy and coherency. The lPPS is generated by a hardware 
divider chain from either the external 1 MHz or the intcrnal 
temperature controlled oven crystal oscillator. A 100 )iz 
digital phase lock loop is c~rrcctrd one microsecond at a time 
to maintain phase lock with the satellite 100 Hz signai. 
Time sigcal outputs provided are: 
Fully syochronizes lPPS output 
Farallel BCD with strobes 
IRIG B Mouulated time code 
IRIG B DC time code 
IZEE 488 I/O interface 
RS 237 I/O int.eriace 
Optional outputs include: 
Additional serial time codes 
Parallel binary codes 
Additional precision raLee 
A list of features are given in Table  1 with a general 
specification following. A block diagraw is in Figure 1. 
REFERENCES 
(1) GOES Satellite Time Code Dissemination by R.E. 
Beehler published in Proceeding of the Fourteenth Annual 
Precise Time and Time Internal (PTTI) Applic~tions and 
Planning Meeting, 
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Model 8600 Satellite Synchonized Generator key features: 
. Continuous Path Delay Correction 
Fully Synchronized 1 PPS Output 
. Internal Drop-In Receiver 
. Microprocessor Controlled 
. Receiver Location Eotered as Latitude and 
Lonqi tude 
. Hardwkre Frequency Divider, Time Acc~rnulator and 
Time Coda Generation Logic 
Displays UTC or Local Time 
. Displays All Set-Up Parameters 
. IRIG B Output 
. Optional Additional Time Code Outputs 
. Parallel BCD Time of Year Output 
. Optional Special Parallel Outputs 
. IEZE-4aa and RSZ32 1/0 Ports 
. Single 1-3/4" Chassis 
, Antenna Supplied 
. Satellite Status Outputs 
RECEIVER: Internal drop-in coherent synchronous digital 
UHF dual conversion receiver with automatic tuning fox 
the reception of satellite generated signals at 468.8250 
MHz and 468.8375 MHz. 
ANTENNA: Outside mast mounted antenna furnished with 
unit. 
SYSTEM SENSITIVITY: The sensitivity is suitable for 
proper operation when the viewing angle exceeds seven 
drgrres above the horizon under normal conditions. 
OPERATION MODES! A CPU suc%ioa supervises internal 
operation and allows the Receiver to synchronize the 
generator only after analyzing the received data for 
acceptable content. Once synchronized, time is 
continuously and smoothly corrected by tkacking the 
received 10" Hz signal and 3y makiny path corrections 
based on received data. Three operating mcdes are 
provided r 
SETUP iSU)r Permits entry of setup data sush as 
latitude, longitude, time zone, preset time. 
GENERATE! Unit generates time, including all rate, time 
code, and computer outputc, without srtmllite time 
synchronization. Time accumulation skartci from the time 
entered during SETUP. 
SYNC: Same as GENERATE except that Receiver provides 
time and frequency updates to the Generator once the 
Receiver is processing acceptable data. 
TIME BASE: The Model 8600 has a~ internal crystal 
oscillator and may also bu operated txom an external 1 
MHz standard. 
INTERNAL FREQUENCY STANDARD: 
Frequency: 10 MHz-9 
Aging rate: k2xlC per day -8 
Temperature stab~lity! i5x10 (0 to 60 deg C) 
EXTERNAL STANDARD INPUT: 
Frequency 1  MHz 
Impedanc,2: 50  ohms 
Amplitude: 0.5 to 10 volts peak-to-peak 
Waveshape: Slnewave ar squarewave. 
TIMEIDATA PRESETTING: Front panel thumbwheel switches 
allows for presetting the time in seconds through days. 
Latitude, longitude, and time zone correction data are 
also entered by these swit.cheo. 
TIME/SETUP/DISPLAYt Nine hiqh-intensity 0.6 inch planar 
LED indicators display time of year in days, hours, 
minutes, and seconds. In the Setup mode, these decimal 
indicators display setup parameters. Decimal points are 
used to indicate operating modes and status. 
TIME CODE OUTPUT: 
Format: IRIG B 122  
Marklsyace ratio! 2rl to Gll adjustable 
LevelsIDRIVE~ Adjustable 1 to 5 VPP into a 50 ohm 
level. 
~ P P S I  OUTPUT! 
Fully synchronized to satellite data clock 
Duty cycle; lo%., POSITIVE-GOINO AT ON TIME 
Levels/DRIVE: TTL levels into r 700 ohm load. 
PARALLEL BCD OUTPUTS: 
Format a BCD time of year in hundreds of 
microseconds through hundreds of days 
Levels/Drive; TTL levels into a 700 ohm load. 
BUILT-IN MONITOR: 
A built in monitor program provides data outputs via both 
IEEE-498 and RS-232 ports. The available output data 
are : 
Time in milliseconds through days 
Time of last synzhronization 
Last delay caiculatign 
Current data being received from satellite 
RS-232 INTERFACE: 
IEEE-488 INTERFACE: ( IEEE-480-1978 CONVENTIONS) 
POWER : 
105 TO 125 VAC 48 TO 440 Hz, 30 WATTS 
PHYSICAL: 
Width : 19 inches standard rack mour.3 
Height: 1-3/4 inches 
Depth : :9  inches 
QUESTIONS AND ANSWERS 
BOB HESSLBERTH, SPECTRACOM: What I s  t h e  p r i c e ?  
M R .  FOSSLER: T h e  i n t r o d u c t o r y  p r i c e  i s  $7,500.  I f  e v e r y  t h i n g  
g o e s  w e l l ,  we e x p e c t  t h a t  p r i c e  t o  d r o p .  T h a t  i n c l u d e s  t h e  
a n t e n n a .  
M R .  BUISSGN: When you s w i t c h  f rom t h e  e a s t  s a t e l l i t e s  t o  t h e  w e s t  
s a t e l l i t e s ,  do  you have  t o  a d j u s t  t h e  a n t e n n a ?  
M R .  FOSSLER: T h e r e  a r e  two ways t o  h a n d l e  t h e  a n t e n n a .  I f  you a r e  
i n  t h e  e a s t e r n  p a r t  o f  t h e  U n i t e d  S t a t e s ,  a n d  p o i n t  i t  i n  t h e  
r i g h t  d i r e c t i o n ,  you g e t  b o t h  s a t e l l i t e s .  If you a r e  i n  t h e  
c e n t r a l  o r  w e s t e r n  p a r t ,  we g i v e  you a  s e c o n d  a n t e n n a  and  you 
w o u l d  s w i t c h  w i t h  a  c o a x i a l  r e l a y  a t  t h e  t i m e  when you s w i t c h  
s a t e l l i t e s .  


New GOES satellite synchronized time code generation

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