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Operations CXO Status Report

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.

------------------------------------------
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

------------------------------------------

All spacecraft subsystems continued to support nominal operations.

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