Subject: DIS blue side down - PLEASE READ

From: Ed Turner

Submitted: Fri, 26 Apr 2002 15:22:54 -0400 (EDT)

Message number: 93 (previous: 92, next: 94 up: Index)

This announcement affects all DIS users for the remainder of this
scheduling quarter and quite possibly extending into 3Q2002.  Please
read carefully.

Due to an unfortunate engineering accident, the blue side of DIS will
be inoperable for an indeterminate length of time, possibly as short
as a month but perhaps up to three months or more.

During reassembly of the blue DIS camera, following installation of a
new field flattening lens and other modifications, an attempt to
dislodge a small piece of foreign matter on the CCD surface resulted
in damage to several of the hair-like "bond" wires on the chip.  We
have sent the CCD back to EEV/Marconi for evaluation; if it can be
repaired, the detector could be returned to service in approximately
4 or 5 weeks.  However, it is quite possible that the CCD is
irreparably damaged.  To ensure that we can recover use of the blue
side of DIS asap, we have placed a rush order with EEV/Marconi for a
replacement detector.  A new CCD typically takes about 14 weeks to
manufacture, test, and install.  We know of no other existing
identical detector that could be obtained on a faster time scale.
Also, it is not possible to reinstall the old DIS blue camera at this
time because of the modifications made during the recent DIS upgrade.

We believe that the red side of DIS is operable, even without the
blue side, but the testing of this will not be completed until later
today.  Assuming that DIS will be usable in red-side-only mode, users
for all scheduled DIS programs should consider the following options:

	1) Use DIS as is, red side only,

	2) Use another instrument for your scheduled science program,

	3) Notify your TAC that you wish to have your time reallocated to
	   another science program, or

	4) If institutional TACs cannot use any time returned to them, it
	   should be declared OPEN asap.

For programs scheduled in May that use DIS (there are no scheduled DIS
programs remaining in April), please must notify your institutional
scheduler and me by e-mail by Friday 3 May with your intentions,
regardless of which option you choose.  For programs whose time is to
be reallocated, the institutional schedulers should notify me of the
program changes as soon as possible.

A call for modifications to scheduled DIS programs in June will be
deferred until we have an assessment of the chances and schedule for
repairing the damaged CCD.

In addition to being posted to apo35-general, this message is being sent
to institutional schedulers and User Cmte members; please make sure that
it is appropriately distributed to affected users at your institution.

DIS is and long has been our most heavily used instrument by a substantial
factor and, with the recent electronics and detector upgrade, is in effect
our newest and most modern instrument.  Every effort is being made to return
its full functionality at the earliest possible date.  Fortunately, a glance
through the observing programs suggests to me that it will be possible to
carry out many of them using the red side only.

If there are any comments or questions, please direct them to me.

Ed Turner

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