Operations CXO Status Report

Friday 27 June 2003 7.30am EDT

During the last week the observing schedule was interrupted following a high radiation event at 4:32pm on Jun 22 that stopped the daily load and activated the science instrument safing sequence (SCS 107). The event occurred just prior to radiation belt entry and is thought to be due to a 'puffed-up' belt state caused by high levels of coronal stream activity. The loads were replanned overnight and science was re-started at radiation belt exit at 10.40am on Jun 23 with 7.5Ks of science loss. The IRU-1 gyro-1 current remained noisy with a base level near 140 mA during the last week. Given the continued elevated current levels and behavior following the warm-restart on Jun 13, the decision has been made to swap to IRU-2 and retain maximum operational lifetime on IRU-1 gyro-1. The swap is expected to be made on July 19 during a suitable comm period and will be made during perigee to ensure no impact to science. Of note last week was the installation of an update to the ground system (ONLS 3.9.3) on June 25 and the conduct of the Cycle-5 Chandra Peer Review during June 24-26. The observing schedule for next week is shown below.

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87GB 1342+5518         ACIS-S       Jun 29
SNR G54.1+0.3          ACIS-I
Radiation Belts                     Jun 30
3C296                  ACIS-S       Jul 1
3C 249.1 Field         ACIS-I       Jul 2
AX J1845-0258          ACIS-S
NGC 1705               ACIS-S
M87                    ACIS-S       Jul 3
Radiation Belts
DEM L71                ACIS-S       Jul 4
AP Librae              ACIS-S
NGC 3631               ACIS-S
Radiation Belts                     Jul 5
DEM L71                ACIS-S       Jul 6

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All spacecraft subsystems, with the exception of the MUPS thruster A-1 under investigation, continued to operate nominally.

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