Status of GPS receiver in AMS02 experiment

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Status of GPS receiver in AMS-02 experiment
AMS Technical Interchange Meeting CERN 27-31
October 2008 Claude Zurbach Laboratoire de
Physique Théorique et Astroparticules -
Montpellier
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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Outline

• New test for cable GPS-receiver lt-gt antenna
• How to manage the GPS constellation almanac ?
• Procedures of activation and monitoring in space
• Next issues

TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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New test for cable
The GPS TopSTar 3000
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
4
New test for cable
Simulation system
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
5
New test for cable
RF cable connection
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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New test for cable
ISS position simulation
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
7
New test for cable
GPS satellites in view
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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New test for cable
How to stress the system ?
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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New test for cable
Display
Init and commands
Procedures
GPS managing (SCS)
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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New test for cable
Channel number
Satellite found 04
What we expect on dispaly ?
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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New test for cable

• Starting the GPS receiver with a procedure giving
  
• the delta between GPS time and UTC time (14s)
• the doppler range, from - 6000 m/s to 6000 m/s
  
• The GPS receiver gets the good resolution in time
  (which need to catch a minimum of 4 satellites)
  in less than 40 minutes.
• After this first result in  snapshot , the
  navigation system of GPS-AMS takes the hand when
  necessary.
• Cable caracteristics
• lenght 2,85 m
• attenuation 0,8 db

TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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How to manage the GPS constellation almanac ?
Every satellite sends the almanac (20 mns to
unload it). Then the receiver stores this
almanac and uses it to anticipate the tracking of
GPS satellites. This almanac will be, in a
regular mode, read by telecommand and saved in
Slow Control System. In case of GPS cold
restart, this almanac will be reload by specific
telecommands in the GPS receiver.
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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The GPS constellation almanac

• To load a GPS constellation almanac in case of
  initialization, improve the behaviour of the GPS
  receiver and divide by 2 the time of precision
  acquisition ( 20 mns)
• Acquisition consists on
• GPS time
• UTC time
• Position x, y, z (useless in case of AMS)

TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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Procedures of activation in space
coldstart-01.tc PPS asserved to UTC time,
STIME telemetry coldstart-02.tc PPS
free-running, STIME telemetry (usefull for

monitoring) warmstart-11.tc PPS asserved,
doppler range, STIME telemetry warmstart-12.tc
PPS asserved, doppler range, time, almanac,
STIME telemetry warmstart-13.tc PPS free
running, doppler range, STIME telemetry warmst
art-14.tc PPS free running, doppler range,
time, almanac, STIME telemetry almanac-unload.
tc GALEPH TC (unloading of complete GPS
constellation almanac) almanac-xxxx.tc
Almanac to load in warmstart-13.tc
14.tc xxxx week number datation
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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Procedures of monitoring in space
monitoring-21.tc TM Snavn, Snavn, Snavi,
Sreceivst, S1/S2/S3rawd, S1chanst,
Stime monitoring-22.tc stop all TM excepted
Stime monitoring-23.tc fusion of
monitoring-21 and 22 with timeout of 600s
between the two procedures
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev
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Summary

• Purchase test and management of GPS receiver to
  improve our knowledge
• Improve interpretation (display) of GPS
  telemetry
• Purchase test of procedures for GPS
  initialization or restarting

Thanks for your attention
TIM 21-27 October 2008 - CERN --- C. Zurbach -
A. Lebedev