CERES aqua instrument simulator for command and upload validation

Three CERES (Clouds and the Earth's Radiant Energy System) Instruments are currently in orbit, one instrument is on the TRMM (Tropical Rainfall Measuring Mission) spacecraft launched in November, 1997 and two instruments are on the Terra spacecraft launched in December, 1999. The Aqua/CERES is scheduled to loft two additional CERES instruments in December, 2000. Three CERES Instrument Simulation Systems have been built which mimic the microprocessor-controlled operational characteristics of each instrument to a high degree. The original CERES engineering development models developed by NASA and TRW Space and Electronics Group were modified to provide the gimballed azimuth and elevation real-time simulation in synchronization with the embedded control processors. The simulators are used to perform testing and functional validation of custom commands and command sequences prior to the actual uploading to the individual orbiting instruments. The architecture of the benchtop simulation hardware matches that of the individual instruments and each operates in conjunction with the associated unmodified TRW developed flight software to assure a virtual reproduction of the performance of each instrument. Performance results of command sequences for calibration maneuvers and other simulation scenarios are presented.