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CERES +15V Power Converter Anomaly

Leonard Kopia

October 16, 1998


  • Operational power was restored to the Clouds and the Earth's Radiant Energy System (CERES) Proto-Flight Model (PFM) instrument aboard the Tropical Rainfall Measuring Mission (TRMM) spacecraft on October 13. A series of specific instrument commands was scheduled over the next six days to obtain temperature and converter voltage information to assess converter operational characteristics. During this time, the converter voltage was observed to rise steadily with temperature, and power was removed at approximately 5:00 AM EDT on October 18, 1998. The TRMM telemetry monitor designed to place CERES in the safe mode (elevation head stowed, azimuth brake applied) and remove operational power was automatically triggered after the Data Acquisition Assembly (DAA) +15 Volt converter exceeded a predefined limit of 18.0 Volts. The 18.0-Volt limit was chosen in order to provide operating margins for components downstream of the voltage converter.

    This action occurred after approximately 4.5 days of instrument operation This operational time provided valuable data that will be used by the CERES Tiger Team in determining the status of the voltage converter (degradation rates and sensitivity) and will aid in planning for future operations to restore the instrument to a science operations mode.

  • An analysis of the internal calibrations conducted on October 17 indicates that the radiometric gains of the three channels have not changed. There is also no indication that there has been any drift in radiometric performance over the first 10 months of mission life.

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