During the last week the Chandra spacecraft executed vehicle-only loads as planned to maintain nominal thermal and momentum status. Following the High Resolution Camera (HRC) power supply anomaly of Feb 9, the HRC continued in a powered-down state, while the Advanced CCD Imaging Spectrometer (ACIS) was safed and in a nominal status. Science observations are temporarily suspended because HRC anticoincidence shield data, which provide a portion of the science instrument radiation protection system, are unavailable.

Real-time procedures were executed on Feb 11 to disable onboard commanding related to the HRC microchannel plate voltage control, and on Feb 17 to uplink a flight software patch to re-configure onboard radiation monnitoring software for deactivation of the B-side HRC channels. Real-time procedures were executed on Feb 17 and Feb 18 to dump OBC memory as a follow-up to the flight software patch earlier on Feb 17. The dump will be used to update the baseline memory images maintained on the ground.

An approach to mitigating risk to ACIS from high radiation environments in the absence of HRC information was developed and approved at a review held on Feb 16. This approach relies on a combination of a software-based radiation monitor in ACIS and a conservative posture toward ground-commanded instrument safing in case of elevated solar storm risk during the science orbit; and a combination of onboard software and insertion of the High Energy Transmission Grating during radiation zone passages. This approach is expected to allow science operations using the ACIS instrument to resume beginning on Feb 21.

HRC Chandra X-ray Center and Instrument Principal Investigator teams in coordination with Flight Operations Team Engineering are continuing investigation of the HRC anomaly in preparation for future diagnostic tests.

Of note this week was the release on Feb 14 of the new web-based Resource Cost Calculator to assist proposers in determining the resource cost (RC) of targets before they create proposals in the Chandra Proposal System (CPS). The RC is a measure of the difficulty of scheduling observations and is one of the limiting factors on how many proposals can be approved to be observed within a cycle.

The schedule of targets for the next week is shown below and includes observations of SwiftJ1818.0-1607, which are follow-ups to a Target of Opportunity accepted on Jul 26, and observations of SDSSJ143016.05+2303, which was accepted as a Director's Discretionary Time Target of Opportunity on Feb 7.