[ASA] temporary suspension of AAT observing

[Warrick Couch]

Dear colleagues:

This is to inform you that observing on the 3.9m Anglo-Australian Telescope (AAT)
has had to be suspended, due to a major failure with the AAT dome shutter. 

Towards the end of last year, it was discovered that a section of one of the
arch girders that support the dome and which the shutter runs along, was
damaged. The most conspicuous evidence of this was a delamination of
the girder, causing metallic flakes (some quite large) to rain down on the
telescope and dome floor beneath. It is almost certain that this can be
attributed to the stiffness of the new dome shutter brake system installed
in 2012, which has put additional stresses on the arch girder as the shutter
moves over it, causing it to deform and the metal to fatigue. As such, an 
engineering company had been contracted to rectify this problem and repair 
the damaged section of the arch girder, with the work scheduled for late April, 
during which observing on the AAT would be suspended for 7-10 days.

However, over this last weekend, the arch girder developed a major crack
in the area where it is damaged, rendering the dome shutter inoperable. 
We have therefore had to suspend observing immediately, and organise
for the aforementioned engineering work to be done as a matter of urgency.
Fortunately the company contracted to do the work can commence this
Thursday (19 March), and are prepared to work extended hours and
through the weekend in order to get the job done as soon as possible.
It is hoped that the job will be completed by next Wednesday (25 March), 
with the AAT operating again very soon thereafter. 

Unfortunately a minimum of 12 nights of observing time on the AAT will
be lost. Steps will be taken to ensure that the scientific programs  
affected will be appropriately compensated for this loss of time. 

I will follow this message up with a second announcement to notify
the community when the problem has been fixed and normal AAT
operations/observing have resumed.

Warrick Couch
(AAO Director)

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Professor Warrick Couch FAA                                Phone: +61 2 9372 4811
Director, Australian Astronomical Observatory   Fax: +61 2 9372 4880
P.O. Box 915, North Ryde, NSW 1760  Email: warrick.couch at aao.gov.au
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