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Operations CXO Status Report

Friday 25 September 2015 9.00am EDT

During the last week Chandra's observing schedule was interrupted by a spacecraft Safe Mode event that occurred at 12:35am EDT on Sep 21. The Safe Mode transition occurred during a scheduled communication pass and resulted in the loss of telemetry. Contact was re-established and a nominal Safe Mode transition was verified. All systems functioned as expected.

The cause of the Safe Mode was a trip of the sun-position monitor. Chandra's scheduled attitude at the time of the trip was very near the position-monitor limit. It is suspected that typical attitude variations (e.g. drift) likely allowed the attitude to go slightly outside of the allowable region, leading to the trip of the Sun Position Monitor. No hardware issues have been identified as contributing to Safe Mode entry. The Chandra Operations team completed the Safe Mode recovery procedure to the prime hardware at 7:00pm EDT on Sep 21. The team completed the clean-up activities, transition to attitude control by pointing at stars, a fine attitude update required to resume science operations following the Safe Mode, and a maneuver to an attitude to prepare for observing at 10:00am on Sep 22. A new mission schedule and loads were approved and began operating at 1:00am on Sep 23. This anomaly resulted in 131.9ks of science loss. Scheduled observations of Haro 11, LP347-5, ArLac, RXCJ0151.6-2900, and 30 Doradus were impacted by the Safe Mode and will be rescheduled.

A Chandra press release was issued on Sep 23 describing observations of Sagittarius A* (Sgr A* for short), the giant black hole at the center of our Milky Way galaxy. A long monitoring campaign of Sgr A* has revealed some unusual activity. Typically relatively quiet, the black hole had an increase in X-ray flares in mid-2014. The timing of this surge coincided with the close passage of the mysterious G2 object near Sgr A*. Astronomers will continue to observe Sgr A* to ascertain the true nature of the increased X-ray activity. For details see:

Of note this week was the release on Sep 23 of CalDB version 4.6.9., ChaRT version 2, and version 4.7.4 of the Contributed Scripts and Modules. The CALDB update includes: new, time-dependent ACIS Gain (TGAIN) files for May-July 2015 (Epoch 62) and updates to the Epoch 61 TGAIN files, newly generated position-dependent gain maps and corresponding RMF calibration files for the back-illuminated ACIS-S1, updates to the Group F ACIS background files, newly calculated line spread functions for HRC-S/LETG observations, and updates to the QE calibration files for HRC-S and HRC-I. ChaRT v2 is an interface to the most recent version of SAOTrace, which includes several changes, most importantly, the ability to account for spacecraft dither which is necessary to perform sub-pixel analysis. The new version of the Scripts and Modules Package fixes a bug in tgsplit affecting CC-mode gratings data and adds several new scripts, including readout_bkg which models the out of time contribution of bright and extended source to the ACIS background. For details see: > and

Also of note this week was the Chandra Quarterly Review conducted on Sep 24 in Cambridge.

The schedule of targets following the recovery from Safe Mode and for the next week is shown below and includes an observation of GRB150518A, which was accepted as a Target of Opportunity on Sep 9.

UDS (2 obs) ACIS-I Sep 23 SNR0453-669 ACIS-S Sep 24 Radiation Belts Sep 25 UDS ACIS-I TPyx ACIS-S Sep 26 2MASXJ03534246+3714 ACIS-S ArLac (21 obs) HRC-I IRAS04124-0803 ACIS-S Sep 27 UDS ACIS-I Radiation Belts 30Doradus ACIS-I Sep 28 UDS ACIS-I TPyx ACIS-S Sep 29 VelaShrapnelDrevi ACIS-I Radiation Belts Sep 30 UDS ACIS-I TPyx ACIS-S Oct 1 GRB150518A ACIS-S SDSSJ073502.30+2659 ACIS-S Oct 2 UDS ACIS-I Radiation Belts UDS ACIS-I Oct 3 TPyx ACIS-S Oct 4 UDS ACIS-I


All spacecraft subsystems continued to support nominal operations.

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