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Friday 12 November 2004 9.00am EST
| Last week the observing schedule was halted due to high radiation
associated with solar flare activity. The loads were halted on Nov 7
at 2:54 pm EST 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. Loads were restarted on Nov 10
at 11.15am however were again halted by SCS 107 autonomously at
11.40am due to high radiation. Shortly after the activation of SCS 107
the spacecraft transitioned to Normal Sun Mode (NSM). Subsequent
analysis explained the transition as due to an unusual timing
combination related to the SCS 107 activation and the configuration
prior to the start of a maneuver. In this case, the the timing of the
momentum transients due the Science Instrument Module motion during
SCS 107 activation resulted in the loss of star lock by the aspect
camera at a time when the Aspect Camera Processing auto-restart was
disabled just prior to the start of a maneuver. The transition to NSM
was expected given the spacecraft configuration for the specific
attitude (sun outside the fine sun sensor field of view). The recovery
from NSM to normal point mode was completed during an extended
real-time pass on Nov 10. An assessment will be made of the
risk/benefit of patching the flight software to handle this unusual
set of conditions in the future.
As a result of the high radiation, the observations from Nov 7-12 will need to be rescheduled in a future load. Radiation levels are now reducing and loads are expected to be resumed at 10:15pm on Nov 12. A Chandra image release was made on 9 November of Chandra and XMM-Newton observations of the red dwarf star Proxima Centauri. The observations have shown that the star's surface is in a state of turmoil. For details see: http://chandra.harvard.edu/photo/2004/proxima/ Once the loads restart, the schedule will be a replanned version of the special two week plan that was to begin on Nov 7. The schedule includes a series of full orbit observations of the Chandra Deep Field South (CDF-S). |
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All spacecraft subsystems continued to support nominal operations.
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Revised: July 08, 2022