Subject: Re: APO 3.5m Shutdown Extension/Mirror Cover damage

From: jegunn

Submitted: Wed, 21 Jul 2004 23:06:32 -0400 (EDT)

Message number: 801 (previous: 800, next: 821 up: Index)

I was very sorry to hear this news; the SDSS may be able to provide some
relief, in that Dave Woods has been working very hard and unsuccessfully
to resuscitate the SDSS camera UPS, fatally damaged in the lightning/power
problems of the previous few weeks. While we would still like very much to
have the UPS fixed (it is an `old-fashioned' unit built by a now-defunct
company which is much better than anything currently available which we
have been able to find) we have found, I think, a satisfactory workaround,
so Dave should feel no pressure from us to perform a miracle on the
UPS; get your work done.

--jim

On Wed, 21 Jul 2004, Ed Turner wrote:

> 
> An unfortunate mechanical accident has damaged the primary mirror covers 
> of the APO 3.5-meter; repairs will require an extension of the in-progress 
> shutdown through August 25 (science operations to resume on the night of 
> August 26).  Contingent and regularly scheduled science programs for the 
> nights of August 7-25, inclusive, are thus canceled.  Details follow:
> 
> During an attempt to close the mirror covers under manual control, either 
> incorrect sequencing of shutters or some other undetermined problem 
> stressed the structure to the point that two rivets were popped loose and 
> numerous others were damaged and greatly weakened.  There was also some 
> damage to the metal surrounding some of the rivets.
> 
> The good news is that there was no apparent damage to the glass or any 
> other components of the telescope and that repair is expected to be 
> reasonably straightforward and simple, though laborious.  The bad news is 
> that these repairs will require removal of the primary and tertiary 
> mirrors, quite substantial and time consuming tasks.  Moreover, the very 
> limited number of personel available at APO to work on the shutdown and 
> the necessity for some of them continuing to concentrate on other tasks 
> (including some associated with the SDSS) limit the rate at which the 
> repair work can be carried out.
> 
> It is not entirely clear yet, but there is also a good chance that it will 
> be necessary to go back into operation without an operational NS2 guider.
> 
> After careful construction of a detailed plan for the repair effort, it is 
> our best ESTIMATE that the telescope will be next available for scheduled 
> science operations on the night of August 26.  Of course, many 
> eventualities (slips in the schedule, discovery of additional problems, 
> weather delays in on-sky recommisioning etc) could affect this date.  
> Updates will be posted here, of course.
> 
> Aside from the accident with the mirror cover mechanism, I am happy to 
> report that the planned shutdown engineering projects have gone well and 
> are essential on-schedule and successful.
> 
> Ed Turner
> 
> 
> 
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