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Operations CXO Status Report

Friday 25 November 2016 9.00am EST

During the last week the Chandra observing schedule was interrupted by an entry to normal sun mode (NSM) at 12:59pm on Saturday, Nov 19 due to the failure to acquire the commanded stars in the aspect camera at the end of a maneuver. The 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 the aspect camera tracked a hot pixel instead of a guide star, which resulted in erroneous values for the on-board estimate of both roll attitude and roll gyro bias. The combined effect resulted in a maneuver error that placed the commanded acquisition stars outside of their search boxes. An analysis of star data prior to the NSM transition indicated that the error was ~179 arcsec. Real-time procedures were executed on Nov 19 to recover from NSM. Loads for a replanned schedule were uplinked on Nov 20 with 110ks of science loss. Observations of Ae Aur and Abell 1795 were impacted by the interruption and will be rescheduled.

In addition to the real-time procedures associated with the NSM recovery, a real-time procedure was executed on Nov 22 to re-initialize the flight software Thruster Command Processing subfunction in order to prevent the occurrence of an overflow condition.

A Chandra press release was issued on Nov 21 describing observations of Cygnus X-3 and its nearby companion nicknamed the "Little Friend", a small dense cloud which reflects X-rays from Cygnus X-3 and is actively giving birth to stars. These observations use Chandra and Smithsonian's Submillimeter Array to capture a snapshot of the stellar life cycle and provide a new way to study how stars form. For details see: http://chandra.si.edu/press/16_releases/press_112116.html

The schedule of targets for the next week is shown below and includes an observation M82 coordinated with NuSTAR.



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V959Mon ACIS-S Nov 28 Radiation Belts Nov 29 G310.6-1.6 ACIS-S Abell1795outskirts ACIS-I Nov 30 V959Mon ACIS-S Dec 1 M82offset2 ACIS-I Radiation Belts Dec 2 ACT-CLJ0248.2+0238 ACIS-I V959Mon ACIS-S ACT-CLJ0248.2+0238 ACIS-I Dec 3 V959Mon ACIS-S Abell1795outskirts ACIS-I G068.23+15.20 ACIS-I Dec 4 Radiation Belts

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All spacecraft subsystems continued to support nominal operations.

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