Friday 28 October 2011 9.00am EDT
During the last week the observing schedule was replanned to include a 20ks observation of GRB111020A that was accepted as a Target of Opportunity on Oct 21. A planned observation of SWIFTJ1749.4-2807 was impacted and will be rescheduled at a later date. The replanned loads were uplinked on Oct 21. The observing schedule was interrupted due to high radiation associated with solar activity. The loads were halted at 2:30pm EDT on Oct 24 through a ground command to execute the SI Safing SCS 107. This ensured that the accumulated radiation dose for ACIS remained below the allowed threshold. A load to handle the Oct 25 eclipse was uplinked on Oct 24. A replanned schedule for resuming science observations was uplinked on Oct 25 with 61.1ks of science loss.
The observing schedule was again halted at 12:58am EDT on Oct 26 by what was likely a single event upset (SEU) in the telemetry processor of the Command and Telemetry Unit, causing a reset of its timing signals and resets of several spacecraft components. An elevated temperature of the aspect camera CCD due to the resets led to its losing track of stars resulting in the spacecraft entering normal-sun mode. All safing actions were nominal.
Recovery procedures were successfully executed Oct 26-27. The tasks included: performing diagnostic dumps of the Control Processing Electronics (CPE), re-synching the on-board computer clocks, re-loading software patches to the aspect camera electronics, to the science instrument module electronics, and to the EPHIN Input/Output unit, resetting the aspect camera CCD temperature, patching the ephemeris-time-offset K-constant in the flight software, recovering to Normal-Point Mode, updating the on-board ephemeris, and performing a momentum dump.
A new mission schedule was uplinked on Oct 27, which resumed science observations at 6:33am EDT on Oct 28, for a 154.0ks of science loss due to the anomaly. The schedule of targets following the anomaly is shown below and includes a follow-up observation of GRB111020A, which was accepted as a Target of Opportunity on Oct 24.
Radiation Belts Oct 28 IC348 ACIS-I BR0351-1034 ACIS-S SPT-CLJ0411-4819 ACIS-I RCS2327.4-0204 ACIS-I 3c19 ACIS-S Oct 29 Vega HRC-I Vega (4 obs) HRC-S Arp256 ACIS-S Oct 30 GRB111020A ACIS-S
Chandra passed through the thirteenth, fourteenth, and fifteenth eclipses of the fall season on Oct 22, 25, and 28 respectively, with nominal power and thermal performance.
Real-time procedures were executed on Oct 27 to dump OBC-A memory as a follow-up to the ephemeris-time-offset K-constant patch. The dump will be used to update the baseline memory image maintained on the ground.
A Chandra image release was issued on Oct 25 describing sample pairs of galaxies that are undergoing close encounters. Close encounters between galaxies may trigger the black holes in their cores to grow rapidly. Astronomers studied thousands of galaxies - some in pairs and others that were isolated - as part of the large COSMOS survey. Results suggest the galaxies in the early stages of an encounter with another were more likely to have actively growing black holes. For details see: http://chandra.si.edu/photo/2011/cid/
A Chandra press release was issued on Oct 26 as a JPL press release describing a multi-wavelength view of the supernova remnant RCW 86. Four space telescopes - Chandra, XMM-Newton, Spitzer, and WISE - combined to make a new discovery on a very old supernova remnant. Chinese astronomers witnessed an event in that location in 185 AD, documenting a mysterious "guest star" that remained for 8 months. The new data show that RCW 86 was created by a Type Ia supernova explosion. This type of supernova is caused when a white dwarf pulls material from a companion star until a thermonuclear reaction occurs. For details see: http://chandra.si.edu/press/11_releases/press_102611.html
Of note this week was the Einstein Fellows Symposium held at NASA's Goddard Space Flight Center in Greenbelt, MD on Oct 25-26. Presentations were made by 26 current Fellows, covering a wide range of topics in observational and theoretical astrophysics research.
The schedule of targets for the next week is still in development and is expected to be reviewed later today.
All spacecraft subsystems continued to support nominal operations.
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