Summary: SI Safing patch uplinked and tested
successfully, operations continued nominally.
Over the weekend, Chandra passed through the radiation belts
and completed observations of M31 to search for Transients and
A2261 with ACIS-I, A2199 and A1835 with ACIS-S, a long
observation of NGC 5548 with the HRC-S and LETG, and an
observation of Cas A with HRC-S. (Please note that the NGC 1068
observation reported in the 12/10 and 12/8 status reports was
observed as planned with ACIS-S and not HRC-S as
reported.)
Following radiation belt exit and ACIS CTI measurement at
2:45pm 12/13, the SI Safing patch uplink and test procedure was
executed. The software patches were uplinked to the spacecraft
during a real-time procedure starting at 2.45pm and completing
at 7.30pm. The patches modify the spacecraft safing actions to
place the ACIS and HRC in protected configurations in the event
of a high radiation environment, unexpected halt of the daily
load or safing action such as bright star hold, normal sun mode
or safe mode. The test procedure was run to check out the
transition to bright star hold, to normal sun mode and to
verify correct action in the event of high radiation triggers
from the radiation monitor (EPHIN). The test was completed
successfully and the modified safing actions are now in place
on the A-side computer. Following final assessment of the dump
telemetry the B-side patches will be uploaded. Two ground
system problems were reported during the test.
During the next 48 hours Chandra will observe TON-S-180 with
ACIS-S/LETG, and LP 944-20 with ACIS-S and ACIS-S/LETG.
The spacecraft systems continued to operate nominally.
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