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Friday 15 August 2008 9.00am EDT
| On 12 Aug Chandra experienced what is believed to be a single event
upset (SEU) in the telemetry processor of the Command and Telemetry
Unit, causing a reset of its timing signals. The Observatory was
slewing between targets at the time of the presumed SEU. The timing
reset slightly modified the end-point of the maneuver, which resulted
in the spacecraft entering normal-sun mode. As a result of the timing
reset, several subsystem hardware items also experienced a reset.
Recovery procedures were successfully executed on 14 Aug to recover to normal-point mode. Prior to running the procedure the ephemeris-time-offset K-constant was patched in the flight software. This patch was necessary for the on-board computer to be able to calculate the position of the Sun for solar array pointing. Chandra was also maneuvered to a cooler attitude as part of the procedure. Following the recovery from normal-sun mode a clean-up procedure was run to re-load software patches to the EPHIN Input/Output unit. Clean-up tasks for the aspect camera electronics, science instrument module electronics, and ACIS had been performed earlier. Science will be resumed this morning at 8:52am. The schedule of targets following the resumption of science and for the next week is shown below. |
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PSR B1957+20 ACIS-S Aug 16 Radiation Belts Aug 18 Carina Clusters Pt ACIS-I Aug 19 2MASSW J1139511-31 ACIS-S Carina Clusters Pt ACIS-I Aug 20 cl2220-5228 ACIS-I J0940-5428 ACIS-I NGC 6681 ACIS-S Aug 21 Radiation Belts WR 140 ACIS-S/HETG MACSJ1931.8-2634 ACIS-I Aug 22 IGR J13135-1109 ACIS-I Aug 23 J1841-0345 ACIS-I NGC 6638 ACIS-S Radiation Belts WR 140 ACIS-S/HETG Aug 24 M81 DwA ACIS-S Holmberg IX ACIS-S Aug 25
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All spacecraft subsystems continued to support nominal operations.
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Revised: July 08, 2022