Subject: 7/95 Eschelle status

From: Ed Turner

Submitted: Fri, 28 Jul 95 13:18:53 EDT

Message number: 1 (previous: 0, next: 2 up: Index)

The attached excerpt of a message from Lew Hobbs (UC) to me summarizes
the current (late July '95) status of the Eschelle.

Ed Turner

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2) I promised to keep you apprised of the status of the echelle spectrograph.
I just obtained today's update, and the punch line is that it's extremely
unlikely that the instrument will be available to users before October 1. With
virtually no risk (unfortunately), you can therefore begin to consider advising
the five TAC chairs to dispose of the echelle time scheduled in September for
their respective observers, in whatever ways we and you see fit. 

3) In brief summary, the echelle problem continues to be what it has been for
a number of months now: "poor" vacuum/cooling performance in the camera
section. A layer of frost continues to form on the (vacant) CCD holder when 
the camera is cooled to the CCD operating temperature. The root cause is said 
to be the large ratio of the warm surface area of the camera housing to the 
cold surface area of the chip. There apparently is only one other camera
known of similar design which has been made to work, after strenuous effort. 
I'm sure that none of us -- including the external expert who attended the
critical design review years ago -- realized that we were sailing into
previously uncharted waters. (No pun intended.)
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