October 27, 1998
PROTO-FLIGHT MODEL CONVERTER TIGER TEAM CONTINUES INVESTIGATION --
- 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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