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Operations CXO Status Report

Friday 15 July 2011 9.00am EDT

Over the weekend engineering analysis determined that the cause of the Jul 6 safemode was the on-board computer using "stale" data in its calculation of the incremental momentum changes that regularly occur. As a result the calculated change in momentum following a maneuver near perigee exceeded the threshold for triggering a safemode, even though the actual change in momentum was well below the threshold. The operational conditions that led to old data being used in the calculation are understood and measures are being put in place to avoid a re-occurrence. Since the safemode was not initiated by a hardware fault, the Chandra Operations team completed the safemode recovery procedure to the prime hardware at 6:30pm EDT on Jul 9. On Jul 10 the team completed the clean-up activities, transition to attitude control by pointing at stars, and fine attitude update required to resume science operations following the safemode. A new mission schedule and loads were approved and began operating at 4:38pm EDT on Jul 11, beginning with an ACIS CTI measurement at the radiation belt exit.

The schedule of targets following the safemode recovery was

       3C402                  ACIS-S       Jul 12
       HD189733               ACIS-S
       SPT-CLJ2145-5644       ACIS-I
       NGC2663                ACIS-S
       31Com                  HRC-I
       2XMMJ120405.8+20134    ACIS-S       Jul 13
       NGC6334                ACIS-I
       Radiation Belts                     Jul 14
       G1.9+0.3               ACIS-S
       A2204_Field2           ACIS-I       Jul 16
       HD189733               ACIS-S
       Radiation Belts                     Jul 17
       J1718-3825             ACIS-S
       NGC6334                ACIS-I


A Chandra image release was issued on Jul 13 describing observations of PSR J0357+3205. A very long tail (over 4 light years across) may be stretching away from this spinning neutron star, or pulsar. The tail is puzzling because it shares characteristics with other tails extending from pulsars, but differs in certain properties. For details see:

Of note this week was the "Structure in Clusters and Groups of Galaxies in the Chandra Era" science workshop being held in Boston, July 12-14.

The schedule of targets for the next week is shown below and includes an observation of Swift J174535.5-285921, which was accepted as a Target of Opportunity on Jul 7, an observation of GRB 110709B, which was accepted as a Target of Opportunity on Jul 12, and an observation of XTE J1710-281 coordinated with RXTE.

 G1.9+0.3               ACIS-S       Jul 18
       HD189733               ACIS-S
       SgrAcomplex            ACIS-I       Jul 19
       Radiation Belts
       NGC0337                ACIS-S
       SGR0418+5729           ACIS-S       Jul 20
       HD189733               ACIS-S       Jul 21
       SwiftJ174535.5-2859    ACIS-I
       SgrAcomplex            ACIS-I
       IGRJ09189-4418         ACIS-I       Jul 22
       Radiation Belts
       G1.9+0.3               ACIS-S
       HD189733               ACIS-S       Jul 23
       1RXSJ165739.1-29494    ACIS-S
       GRB110709B             ACIS-S
       XTEJ1710-281           ACIS-S/HETG
       1RXSJ180408.9-34205    ACIS-S       Jul 24


All spacecraft subsystems continued to support nominal operations.

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