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Date: Mon, 3 Sep 2007 18:04:16 -0400 (EDT)
From: Kenneth Sembach
Subject: HST Status - 2 Gyro and NICMOS updates


Good Evening Everybody,

As you've heard, Gyro 6 was turned on over the weekend to replace
Gyro 2, which has failed and is no longer usable. (As Rodger Doxey's
earlier email to the staff indicated, the observatory responded
to the failure as planned.) The Gyro 6 restart proceeded as planned, and
the gyro is performing well. Several guide star acquisitions have been
performed successfully with the new gyro pair (Gyros 1 and 6), and so far
the pointing control looks good. The Pointing and Control Systems
group at GSFC continues to monitor progress with the gyros.


We successfully executed the science loads for the coming week
last night. This put HST back on a science timeline to do
science with the WFPC2 this week. I'd like to thank the
Planning and Scheduling teams, the Commanding teams, and everyone
else here at the Institute who gave up their holiday weekend
to prepare this science intercept and the health and safety loads
required prior to the resumption of science activities. It is
wonderful to to have such dedicated people here and at GSFC
watching over HST.

This Saturday at 10:59 PM we also experienced an unexpected
safing of NICMOS. The safing event occurred after the return to 2-gyro
operations and does not appear to be related directly to the
2-gyro issues of the past few days. Initial investigations of the
telemetry indicate that one of the data buffers that reports internal
engineering status of the instrument to the main spacecraft computer
did not contain an expected telemetry value. As a result, the
instrument was safed, which is the proper response to this condition.
NICMOS was not obtaining science data at the time of the safing. The
HST engineering teams and the STScI are discussing options for bringing
NICMOS back on line as soon as possible. The timeline for doing so
will be discussed at an engineering briefing early Tuesday morning.
Presently, no NICMOS observations are scheduled for this week, but this
too may change depending upon the chosen path forward.

ACS, WFPC2, and the FGSs are operating nominally at this time.

I will provide another update tomorrow as more information becomes
available. We will also be posting updates on HST status
on the STScI website on Tuesday to inform the user community of
these recent developments. I ask for your patience and
restraint in forwarding this email as we have procedures for
notifying the observing community in a coordinated manner with the
HST Project through several channels. Rest assured, we will
keep everyone informed as useful information becomes available.

Stay tuned,
Ken