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Operations CXO Status Report

Monday 27 September 1999 7.00am EST

During the last 24 hours the spacecraft experienced a bright star hold and safe mode event. Following trouble shooting and assessment, the spacecraft was returned from safe mode to normal Sun mode and readied for the next eclipse scheduled at 12:30PM 9/27. The ACIS was commanded to the next-in-line position for radiation belt passage. During the safe mode entry and recovery to normal sun mode the spacecraft performed as expected.

The spacecraft entered bright star hold at 9AM 9/26 following a maneuver with a large attitude error due to an incorrect quaternion in the command load. Safe mode entry occurred at 6:57PM 9/26 following an operator error during fine attitude initialization to recover from bright star hold. Safe mode recovery to normal Sun mode was completed at 4:10AM 9/27. Full analysis is being performed on the sequence of events leading to safe mode, however initial assessment indicates modifications to flight and ground software and ground procedure are required.

Following fine attitude initialization, the plan is to re-intercept the GTO observing plan after appropriate load review and procedure revision.

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