THEMIS IDPU Software Requirements
THM_FSW_001A
Peter R. Harvey
University of California, Berkeley
Revision -
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Table of Contents
1.
INTRODUCTION ................................................................................................................................ 3
1.1 RELATED DOCUMENTS ......................................................................................................................... 3
2.
DATA RATES ...................................................................................................................................... 4
3.
DATA STORAGE ................................................................................................................................ 5
4.
FAULT PROTECTION ....................................................................................................................... 6
5.
INSTRUMENT ACCOMODATION.................................................................................................. 7
6.
TIMING ................................................................................................................................................ 8
Change Record
9-30-2003
10-12-2003
Initial Version
Removed reference to moment calculations which are performed in ETC Actel.
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1. Introduction
The following documents the requirements for flight software for the THEMIS
Instrument Data Processor Unit. Changes to this document are controlled by the
THEMIS Systems Engineer.
The flight software requirements have been derived from the Mission
Requirements Document (MRD version 17). The FSW specification is contained
in the (hsi_fsw_002) document. It includes details of the implementation of the
software and is updated as the software is written.
In this document, FSW will refer to Flight Software of the Instrument Data
Processor and is not to be confused with the Probe Flight Software.
1.1 Related Documents
These documents are available on the web at:
ftp://apollo.ssl.berkeley.edu/pub/THEMIS/
[1] thm-sys-001
[2] thm_fsw_002
THEMIS Mission Requirements Document
THEMIS Flight Software Specification
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2. Data Rates
•IN.FSW-1. The IDPU FSW shall receive commands from the C&DH Subsystem
via a 38.4 kbaud bi-directional interface (Ref IN.DPU-1).
•IN.FSW-2. The IDPU FSW shall send telemetry to the C&DH Subsystem via a
38.4 kbaud bi-directional interface(Ref IN.DPU-2).
•IN.FSW-3. The IDPU FSW high speed interface (science data) to the C&DH
Subsystem shall be at multiple fixed (commandable) rates from at least 1 kbps to
2 Mbps (Ref IN.DPU-3).
•IN.FSW-4. The IDPU FSW shall be able to provide a real-time engineering data
stream at the minimum data rate possible (1kbps). (Ref IN.DPU-4).
•IN.FSW-5. The IDPU FSW shall provide loss-less data compression (nominal 2x
reduction) for all instrument data. (Ref IN.DPU-5).
••Rationale: Data rates driven by requirement to downlink all science and
housekeeping data within 30 minute/day transmitter-on power constraint. Power
constraint and bandwidth allocations drives on-board data compression. Multiple
data rates ensures positive link margin for all probes during all parts of orbit.
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3. Data Storage
•IN.FSW-6. The IDPU FSW shall provide sufficient storage for all instrument
science and housekeeping telemetry in SRR when not in ground contact:
750Mbits/orbit uncompressed + 1 day for contingency(Ref IN.DPU-6).
•IN.FSW-7. The IDPU FSW shall be capable of playing back data upon
command during ground contact (pointer from operators) (Ref IN.DPU-7).
•IN.FSW-8. The IDPU FSW shall provide the capability to re-transmit the SSR
contents(Ref IN.DPU-8).
•IN.FSW-9. The IDPU DCB shall not erase instrument housekeeping telemetry
from memory unless commanded to do so (Ref IN.DPU-9).
••Rationale: Storage sufficient to downlink all science data collected. Storage
architecture accommodates operations concept not to overwrite data on-board
until valid data receipt on the ground is confirmed (i.e. neither transmittal to
ground or reset should not erase memory)
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4. Fault Protection
•IN.FSW-10. The IDPU FSW shall validate commands prior to execution(Ref
IN.DPU-10).•IN.FSW-11. The IDPU FSW shall implement autonomous fault
protection features to ensure the health and safety of the instruments(Ref
IN.DPU-11).
•IN.FSW-12. The IDPU FSW shall enable all autonomous functions to be initiated
and disabled by ground command(Ref IN.DPU-12).
•IN.FSW-13. The IDPU FSW shall provide separate enable and activation
commands for critical instrument functions such as boom deployments(Ref
IN.DPU-13).
•IN.FSW-14. The IDPU FSW shall provide the capability to upload or modify
Instrument flight software. (Ref IN.DPU-14).
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5. Instrument Accomodation
•IN.FSW-15. The IDPU FSW shall accommodate continuous instrument data
governed by overall system mode (Slow Survey, Fast Survey, Particle Burst,
Wave Burst I or II). Modes selected by ATS command or on-board triggering
logic. (Ref IN.DPU-15).
•IN.FSW-16. The IDPU FSW shall provide engineering telemetry sufficient to
safely turn-on and operate all instruments (temperatures, currents, voltages, and
bi-levels) as defined in Instrument-IDPU ICDs(Ref IN.DPU-16).
•IN.FSW-17. The IDPU FSW shall provide operational commands and test
programs for all instruments as detailed in the Instrument-IDPU ICDs (Ref
IN.DPU-17).
•IN.FSW-18. The IDPU FSW shall provide initialization parameters to the
Instruments as detailed in the Instrument-IDPU ICDs(Ref IN.DPU-18).
•IN.FSW-19. The IDPU FSW shall provide in-flight data processing as detailed in
the Flight Software Specification (includes spin fits, spin sectoring) (Ref IN.DPU19).
•IN.FSW-20. The IDPU FSW shall provide Instrument thermal control if
necessary (PWM) (Ref IN.DPU-20).
•IN.FSW-21. The IDPU FSW shall provide FGM telemetry to the Probe C&DH
Subsystem at a sample rate of 1 Hz (Ref IN.DPU-21).
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6. Timing
Spin-Based Data Transfer
•IN.FSW-22. The IDPU FSW shall read the time of the received raw sun pulse
signal from the Probe to 16-bits of accuracy (Ref IN.DPU-26).
•IN.FSW-23. The IDPU FSW shall strongly filter the raw sun pulse signal and
provide a once-per-spin reference pulse (SRP) to the SST and ESA(Ref IN.DPU27).
•IN.FSW-24. The IDPU FSW shall distribute a Spin Sector Clock with 2^14 phase
pulses per spin to the ESA and SST (synchronized with the SRP) (Ref IN.DPU28).
Time-tagging
•IN.FSW-25. The IDPU FSW shall receive Universal Time (UTC) from the Probe
(Ref IN.DPU-29).
•IN.FSW-26. The IDPU FSW shall use UTC to time stamp instrument telemetry
(Ref IN.DPU-30).
•IN.FSW-27. The IDPU FSW shall time-tag ESA and SST Spin Reference Pulse
(SRP) to <0.5 ms (Rationale: 0.83 ms = 0.1 degree at 3 second period) (Ref
IN.DPU-31).
•IN.FSW-28. The IDPU FSW shall time-tag DFB and FGM data to < 2 ms (Ref
IN.DPU-32).
Synchronization•IN.FSW-29. The IDPU FSW shall obtain time (UTC w/sub
seconds) from the Probe C&DH Subsystem to synchronize Bus and Instrument
clocks. (Ref IN.DPU-33).
•IN.FSW-30. The IDPU FSW shall coordinate ESA and SST synchronization by
sending spin count to these systems. (Ref IN.DPU-34).
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Safety
•IN.FSW-31. The FSW shall include safety inhibits to prevent accidental high
voltage turn on to the ESA and SST(Ref IN.DPU-49).
•IN.FSW-32. The FSW shall include safety inhibits to prevent accidental
deployment of the booms(Ref IN.DPU-50).
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