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Friday 28 September 2001 12.00pm EDT
| During last week the observing schedule was interrupted after the Observatory entered a bright star hold at 7.48am on Sept 22. The entry followed a 2.5 hour observation of the dark moon performed on gyro-hold. Analysis of the dump data indicates that a gyro bias error of ~170 arcsec accumulated during the gyro hold and subsequent maneuver. The error exceeded the size of the aspect camera search box during the next star acquisition and resulted in the bright star hold. Data indicates that the gyro performance remains consistent with past performance, however a detailed analysis will be performed by the gyro vendor. Fine attitude was recovered at 11pm EDT on Sept 22, and loads were uplinked at 2pm on Sept 23. The observations of Comet 19P/Borrelly, Puppis N Knot and 1RXS J1708-4009 were impacted by the bright star hold.
The loads were interrupted a second time at 10.29am on Sept 24 by a significant solar radiation event that stopped the daily load and activated the science instrument safing sequence (SCS 107). All actions were nominal and assessment of the dump data confirmed that the trigger was due to high proton counts in the EPHIN E1300 channel exceeding the pre-defined threshold of 10 counts/cm^2/s/sr. The solar levels have remained high throughout the week but are projected to reach an acceptable level during Sept 29. The loads are planned to resume at 12.50am on Sept 30. The 10 observing targets impacted by the radiation event will be rescheduled in a future load. The schedule for next week is shown below. |
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SGR 1627-41 ACIS-S Sep 30 IRAS 23128-5919 ACIS-S Puppis A shock front ACIS-S Oct 1 Radiation Belts CAL 83 HRC-S/LETG Oct 2 UV CETI,GLIESE 65 HRC-S/LETG IRAS 05189-2524 ACIS-S Oct 3 Puppis bright E knot ACIS-S Radiation Belts Oct 4 ABELL 496 ACIS-S M31 Nucleus ACIS-S M31 Nucleus ACIS-I Oct 5 A2556 ACIS-S SAX J1753.5-2349 ACIS-S XTE1650-500 ACIS-S/HETG NGC6093 ACIS-S Oct 6 Radiation Belts RCW103 ACIS-S Oct 7 PKS 2135-14 ACIS-S
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All spacecraft subsystems continued to operate nominally.
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Revised: July 08, 2022