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CERES +15V Power Converter Anomaly

Leonard Kopia

October 27, 1998


  • The Tiger Team investigating the converter anomaly observed on the Clouds and the Earth's Radiant Energy System (CERES) Proto-Flight Model (PFM) on board the Tropical Rainfall Measuring Mission (TRMM) continues in its attempt to isolate the root cause. Data from the interim turn-on (October 13-18) indicates that the onset of unregulated converter operation occurred at a lower temperature than that which occurred on September 1 (the last powered operation of the instrument). This suggests a degradation has occurred over the time that the instrument was off (approximately 40 days). The instrument will be powered up once again in early November to place the instrument in a protected position to minimize any detrimental effects from passing through the Leonid shower in mid-November. Data from that operational sequence will be used to confirm degradation rates for the converter and provide information for future operational scenarios.

  • No specific cause for the converter anomaly has yet been determined but several possibilities are being considered seriously. The strongest possibilities include: deterioration of the feedback opto-coupler, including possible electrical and physical changes of the bonding material used to hold it in place; and, a possible cracked resistor in the gain control loop which has become thermally dependant and is degrading. Other lesser possibilities also exist and are being thoroughly examined for their relevance.

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