Friday 1 August 2014 9.00am EDT
Chandra entered Normal Sun Mode (NSM) at 3:03am EDT on Saturday Jul 26 due to the failure to acquire the commanded stars in the aspect camera at the end of a maneuver. Entry into NSM was nominal and an assessment of the telemetry indicated that all spacecraft hardware was performing nominally. The most-likely cause for failing to acquire stars is that a gyro-bias excursion occurred during the maneuver, which resulted in a maneuver error that placed the commanded acquisition stars outside of their search boxes. An analysis of star data that did appear in the search boxes prior to the NSM transition suggests that the error was ~200 arcsec, which is consistent with previously seen gyro bias excursions. The failure to acquire the commanded stars would usually result in a search for bright stars in the aspect camera field-of-view but since Chandra's pitch angle placed the Sun outside the Fine Sun-Sensor field-of-view Chandra transitioned to NSM. A real-time procedure was executed on Jul 26 to configure Chandra for eclipse entry while in NSM. Chandra passed through the eclipse (the sixth of the season), with nominal power and thermal performance. Additional real-time procedures were executed on Jul 26 to recover from NSM to pointing at stars and to initiate a long ACIS CTI data collection while waiting to return to observations. Loads for a replanned schedule were uplinked on Jul 27 with 99.3ks of science loss. A planned observation of IGR J17062-6143 was impacted by the interruption and will be rescheduled.
Chandra passed through the seventh and eighth eclipses of the season on Jul 29 an 31 respectively, with nominal power and thermal performance.
A real-time procedure was executed on Aug 1 to swap the prime solid-state recorder (SSR) from the A-side to the B-side. It is planned to swap the prime SSR between the A- and B-sides every six months in order to obtain health and trending data on both SSRs for the remainder of the mission.
The schedule of targets for the next week is shown below and includes an observation of SS 433 coordinated with the VLBA.
OphiuchusCluster ACIS-I Aug 4 EtaCarinae ACIS-S XMMUJ122939.9+07533 ACIS-S ChandraDeepField-S ACIS-I Aug 5 J224024.1-092748 ACIS-S Radiation Belts ChandraDeepField-S ACIS-I Aug 6 EtaCarinae ACIS-S Abell1703 ACIS-I Aug 7 J205058.0+055012 ACIS-S OphiuchusCluster ACIS-I Aug 8 Radiation Belts OphiuchusCluster ACIS-I Aug 9 SS433 ACIS-S/HETG
All spacecraft subsystems continued to support nominal operations.
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