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CTIO Instrumentation (1Mar94)
(from CTIO, NOAO Newsletter No. 37, 1 March 1994)

During the past quarter we generally have been successful in
concentrating our engineering resources on our three top-priority areas
for improvements: the package of optics and seeing improvement projects
for the 4-m; development and implementation of ARCON CCD controllers;
and work on the IR instrumentation.

Important progress was made in the image improvement program at the
4-m.  A separate article describes the results of repolishing the f/8
secondary.  Not described there is a sizeable project to improve the
controllability of the focus and alignment mechanism for this
secondary.  The old motors and drives were replaced by a system
consisting of three jack screws under precise computer control.  The
upgrades were completed while the mirror was being repolished, and will
be an important component of our eventual active optics system for the
4-m.

We also put our 4-m primary mirror cooling system into routine daytime
use.  This system draws in air from inside the dome, cools it using a
heat exchanger connected to the building's air conditioning system, and
then blows the cold air up through the (unused) coud light path and
into the mirror cell.  A computer keeps the cooled air at a preset
temperature which is a few degrees below the expected nighttime air
temperature, and shuts the system down when the humidity gets too
high.  We are successfully cooling the mirror enough so that as it
reheats during the night its outer skin seldom gets above the ambient
air temperature.  We have not yet made the extensive measurements
needed to gauge the effect on seeing.

There has also been good progress with the ARCON CCD controllers.  At
the start of the quarter we had ARCONs running with four older CCDs
which had been transferred over from the VEB controllers.  The ARCONs
are now in a sufficiently developed state that we are able to start
bringing up new CCDs with them.  Three are now in progress.

The first new CCD is a thinned Loral 3K x 1K which will be used in the
Air Schmidt camera on the 4-m R-C spectrograph.  We are hoping to have
this ready to go in April, although it is touch and go.  Once in use,
this CCD will give us roughly a factor 2 increase in QE over the
Reticon CCD that we presently use.

The second CCD now being characterized is a Tektronix 2048 x 2048 for
the WIYN telescope.  This is being brought up by Andy Rudeen, who is
visiting CTIO from KPNO.  Work is well along; the controller presently
produces images with an engineering grade chip.

In addition, CTIO has obtained a new Tektronix 2048 x 2048 CCD,
reportedly with much better cosmetics than our existing Tek 2K.  This
chip will be used for direct imaging and with the 4-m and 1.5-m echelle
spectrographs.  We have also made good progress with the ARCON for this
chip, and hope to have it on the air by the middle of the year.

A fourth new CCD is in the queue, but work will not start on it until
late in the year.  It is a thinned Loral 1200 x 400, and will be
dedicated to the 1.5-m Cassegrain spectrograph.

Two important IR instrumentation projects are now in full swing.  The
first is the conversion of the Infrared Spectrometer (IRS) to a 256 x 256
array.  The array will be controlled by the KPNO WILDFIRE system,
so most of the work will be done by the KPNO IR group.  The second
project is the construction of our new NICMOS imager, which will also
use a 256 x 256 array, also controlled by WILDFIRE.  This is the major
mechanical project now occupying our machine shop.  Both of these
instruments should see first light in July.  Actually, it will be third
light in the case of the IRS, which has seen its share of upgrades.
More details are given in an accompanying article.

Finally, we moved the console room of the 1.5-m.  Or, more accurately,
"they" moved it... this author can't find it anymore, and has gotten
tired of looking for it.  But it's rumored to be approximately one
floor lower than it used to be, in a location offering much better
thermal insulation from the telescope chamber.  The new console is also
larger and better laid out.

Jack Baldwin

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