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Operations CXO Status Report

Friday 9 November 2001 3.30pm EST

Last week the observing schedule was interrupted following a high radiation event at 1:37pm EST on Nov 4 that stopped the daily load and activated the science instrument safing sequence (SCS 107). All actions were nominal and assessment of the dump data confirmed that the trigger was due to high proton counts in the EPHIN E1300 channel exceeding the pre-defined threshold of 10 counts/cm2/s/sr. Radiation levels allowed the loads to be restarted at 3pm on Nov 8.

The loads were interrupted a second time at 10am on Nov 9 to accommodate a high priority Target Of Opportunity received late on Nov 8. The target, XRF010930, is a candidate for the first X-ray observation of a fast X-ray transient.

A recurrence of the ACIS threshold crossing plane latchup occurred on Nov 4 just prior to the SCS 107 trip (un-related) and a real-time recovery procedure was completed on Nov 6. The latchup is thought to occur under specific ACIS operating conditions and work is underway to establish criteria for avoiding future latchups.

Preparations were completed last week for the uplink of a flight software patch to decrease the momentum unloading dead-zone from 6 to 2 ft-lb-sec. The momentum auto-unload threshold will also be commanded from 27.9 to 31.9 ft-lb-sec. The procedure will be conducted on Nov 12 at 8pm. The new values will expand the momentum envelope and result in a reduced number of Momentum Unloading Propulsion System warm start firings.

Preparations were also completed for passage of the 2001 Leonids meteor shower on Nov 18-19. Chandra will be pointed in the anti-radiant direction during the passage and will be placed in a gyro-hold for approximately 3 hours during an Earth-occultation that occurs during the same period. Contingency procedures have been identified and prepared, and the engineering team will be on console during the event.

The schedule of observations starting with the TOO and for the coming week is shown below and includes a series of observations of the Hubble Deep Field North.

------------------------------------------
FXRT011030 TOO          ACIS-S       Nov 9
Radiation Belts                      Nov 10
AX J0836.2+5538         ACIS-S
AX J0836.6+5529         ACIS-S
NGC 3516                ACIS-S/HETG
MACS-J0744.8+3927       ACIS-I       Nov 11
RXJ0806.3+1527          ACIS-S       Nov 12
MACSJ0257.6-2209        ACIS-I
Radiation Belts
PSS 0902+1640           ACIS-S       Nov 13
HDF-N                   ACIS-I
Radiation Belts                      Nov 15
HDF-N                   ACIS-I       Nov 16
V 410 Tau               ACIS-S
HDF-N                   ACIS-I
NGC 7252                ACIS-S       Nov 17
Radiation Belts                      Nov 18
NGC 7099                ACIS-S

------------------------------------------

All spacecraft subsystems continued to operate nominally.

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