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Operations CXO Status Report
Monday 5/22/00 8:30am EDT
During the last week, Chandra completed the observing schedule as
planned.
This week's loads were rebuilt on 5/15 after noting a failure to
acquire 3 of the 5 acquisition stars for an observation (Q0059-2735)
on 5/15. Acquisition Stars had also been dropped by the Aspect Camera
on a number of other observations over the weekend. If the number of
stars acquired falls below 2 then the spacecraft will stop the daily
load and transition to bright star hold. Engineering assessment
indicated that the aspect camera performance had not changed, and that
the likely cause was a recent change to the parameters used by the
OFLS in determining the faint limit for acquisition stars. The change
was made in conjunction with the installation of a new star catalog
and was based on analysis of prior on-orbit data. The loads for the
remaining part of the week were rebuilt using an increased error term
to avoid the possibility of a bright star hold. The loads were
uplinked without impact to spacecraft operations, and the remaining
acquisitions for the week were made as expected. Further analysis is
underway to determine the optimal error terms for use by the OFLS.
The first HETG insertion and retraction commanded from the daily load
using the B-side MCE was completed successfully for the 5/18
observation of Ex Hya. Telemetry indicated that both the insertion and
retraction were nominal. Operations will continue using the B-side MCE
while other approaches for returning A-side redundancy are assessed.
Preparations were completed for the 4th ACIS Squeegee mode test
scheduled for 5.30pm EDT on 5/22. This test will include initial
flushes of the CCD to remove charge built up while the CCD is not
being clocked in order to remove a bias instability seen during the
earlier on-orbit tests. Two runs will be performed: a 16 row squeegee
with a 32 row exclude window, and a control run.
The planned observations for the coming week are as follows.
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PSS 1435+3057 ACIS-S May 21
Cen Cluster ACIS-S
BHXB (Outburst Decay) ACIS-S/HETG May 22
Radiation Belts
NGC 6652 HRC-I
NGC 6441 HRC-I
Ophiuchi Mosaic #4 ACIS-I May 23
1735-269 ACIS-S
G21.5-0.9 (a series) ACIS-S
NGC 5846 ACIS-S May 24
Radiation Belts
Abell 2104 ACIS-S May 25
1217+301 HRC-I May 26
Cygnus A ACIS-S
M31 (N, S, Center) HRC-I
Q2345+007 ACIS-S
AXAF Southern Deep Fld ACIS-I
Radiation Belts May 27
E0102-72.3 ACIS-S May 28
Q1127-145 ACIS-S
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All spacecraft subsystems continued to operate nominally.
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