Friday 14 August 2009 9.00am EDT
|During the last week Chandra completed the observing schedule as
A real-time procedure was conducted on August 10 to uplink a flight software patch to the OBC grating insertion/retraction code to avoid using the state of the faulty HETG retract limit switch. This patch is to resolve the July 7 anomaly in which the OBC grating "move failed" flag was set. The real-time procedure also cleared the flag. Completion of this procedure re-enables the use of the gratings for observations. A follow-on real-time procedure was conducted on August 13 to perform a routine dump of the OBC memory to maintain a ground record of the on-board version.
In response to the ongoing MUPS tank anomaly investigation, a real-time procedure was conducted on August 12 to enable automatic momentum unloads if the spacecraft angular momentum exceeds 40 ft-lb-s. The step was taken as a precautionary measure in the event that the pressure drop is due to a leak, and provides an auto unloading capability as an early level of protection against a leak-induced momentum disturbance instead of relying on safe-mode.
The investigation into the cause of the MUPS tank pressure reading drop has continued with the prime candidate for the root cause thought to be faulty sensor readings but with a leak not ruled out. Since the drop in readings appeared to increase with temperature of the MUPS, spacecraft attitudes have been restricted to those that minimize the temperatures of the MUPS tank and fill panel. This restriction of attitudes has necessitated modification of the planned long-term schedule and resulted in the earlier than expected use of cycle 11 targets, requiring extensive coordination with observers. The engineering team is developing detailed plans and products for performing a firing of the MUPS thrusters in order to measure the impulse that they generate as a secondary determination of the MUPS tank pressure.
A Chandra image release was issued on August 12 of Cepheus B. The composite image, combining data from the Chandra X-ray Observatory and the Spitzer Space Telescope shows the molecular cloud Cepheus B, located in our Galaxy about 2,400 light years from the Earth, a place where stars are known to form. For further details see: http://chandra.harvard.edu/photo/2009/cepb/
On August 13 the CXC launched a redesigned version of the top-level science web page: http://cxc.harvard.edu
The schedule of targets for the next week is shown below
ESO243-49HLX-1 HRC-I Aug 17 Radiation Belts Abell2631 ACIS-I Aug 18 A2645 ACIS-S Abell2627 ACIS-S PSRJ1907+06 ACIS-S Aug 19 4U1901+03 ACIS-I NGC6868 ACIS-I Radiation Belts Aug 20 ES1-351 ACIS-S UGC408 ACIS-S Aug 21 SN2001em ACIS-S Aug 22 Radiation Belts Aug 23 IRAS00397-1312 ACIS-S
All spacecraft subsystems continued to support nominal operations.
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