GP-B Post-Flight Analysis—Final Report - Gravity Probe B - Stanford ...

Appendix E, Flight Software Applications SLOC lists the source lines of code (SLOC) for the various FSWapplications and their sub-components. 59,000 lines of ADA and 2.3 MB of memory were required toimplement the FSW features required by GP-B. At run time, the FSW expands to 3.5 MB in the CCCA SRAMafter heap, stack, an other dynamic storage is allocated.Detailed requirements and functional descriptions of the FSW components can be found in Lockheed MartinDocument #P086580: SCSE-15, Gravity Probe B Flight Software Requirements Specification.8.5.3 Test It Like You Fly ItAll of the GP-B software (Mission Support, Payload, and Ground) was tested in the Integrated Test Facility(ITF) during the Formal Qualification Test (FQT) phase of the mission; one of the requirements to pass theFlight Readiness Review prior to launch approval. The ITF is a static, on-ground spacecraft simulator thatcontained engineering models or flight equivalents of spacecraft and payload subsystem, a vehicle dynamicssimulator computer to test the attitude and translation control system, and a communications downlinkprocessor to permit the vehicle to communicate with the MOC our flight interfaces. Figure 8-35 shows a pictureof the ITF hardware as configured late in the mission.The FQT was performed using the flight approved command templates (except where ITF-specific versionswere required to account for differences between the ITF and the on-orbit Space Vehicle environment) in anapproved manner in a series of about 15 comprehensive tests. The testing process of loading a series ofcommand templates and executing them sequentially based on time-tags was the same process used during onorbitoperations. The same tools are used to construct the command loads for testing as for operations. Thesame ground station software is used to uplink commands and command loads, to start execution of thecommand loads, and to monitor and record the telemetry for testing as for operations.The ITF was used prior to launch to test the flight software and to test the command templates used for on-orbitoperations. After launch it was used to test any new or changed command templates as well as to check theoperation of all new real-time command scripts, such as those used to clear multi-bit errors. Also after launchthe ITF played a key role in the regression testing necessary to confirm that the post launch software changeworked as specified with no surprises. It also was used to test the process of loading and rebooting the flightsoftware prior to using the process on the space vehicle.242 March 2007 Chapter 8 — Other Spacecraft Subsystems Analyses