Previous Article
Next Article
Table of Contents

CCD News (1Jun92)
(from CTIO, NOAO Newsletter No. 30, 1 June 1992)

In June we will begin the conversion from operating our CCDs with the
VEB controllers to using the new Arcon controllers. This change-over
process will continue for some 18-24 months by which time all our CCDs
and some of the IR arrays will be operated by the Arcons, and much
ancient hardware (VEBs, LSIs) and software (Forth) will have been
retired. As far as the CCDs are concerned, the conversion is
complicated by the VEBs being telescope-based whereas the Arcons are
dewar-based. Thus, if we wish to retire a VEB off some specific
telescope, we must ensure that all the CCDs we want to use on that
telescope are first converted to Arcons, or else accept some smaller
number of options. In addition, we do not want to impair significantly
the rate at which we are able to commission new detectors, since over
this period we are expecting another Tektronix 2048, a Reticon 1200 x
400, and several Loral CCDs. As we proceed, we will retire the last of
our EEV (GEC) CCDs and the Thomson 1024s.

At the moment, we are operating a Thomson CCD at the Schmidt telescope
(see Newsletter No. 29, page 15) with the prototype Arcon 2.1. This
system is being shared for development work, but shortly the R&D will
move to Arcon 3.1, which will also use a Thomson CCD. The latter will
be a lab system only, employed for testing and verifying boards for the
Arcons as they are produced. Arcon 3.2 will operate a Tek 1024, and
Arcon 3.3 a Tek 2048. Both these CCDs have four low noise amplifiers
and will benefit greatly from the quad readout capability of the
Arcons. The change-over will also eliminate the difficulty of operating
these mega-pixel arrays with the LSI 11/73 computers. Arcon 3.4 is
destined for the NICMOS III HgCdTe IR array.

As soon as Arcon 3.2 is operating, we will retire the 0.9-m VEB, which
will then become a spare for the VEBs remaining at the 1.5-m and 4-m
telescopes. As a consequence, for a period of about two months next
semester the Tek 1024 CCD will be the only CCD available at the 0.9-m,
except for programs where U band sensitivity is paramount or where
there is a clash with the 1.5-m or 4-m schedules. For these cases we
will schedule the Thomson CCD from the Schmidt. We will try to juggle
the 0.9-m schedule with the exact date of the VEB removal so that there
is as little conflict as possible with people's programs. At the end of
this two month period, the Tek 2048 will have also been converted to
use an Arcon and will thus become available at the 0.9-m. However,
users should be aware that TI and Tek 512 CCDs will not be usable at
the 0.9-m for at least a year. We are sure that present users of the
Tek 512 will be more than happy with the Tek 1024/2048 due to the much
improved region-of-interest handling and the quad readout compensating
for the longer readout time of the bigger CCDs.  The TI CCDs are
presently only used for the few programs where the U band sensitivity
is of the utmost importance.  There will unfortunately be a period of
time where we will not be able to offer a CCD at the 0.9-m which has as
good a UV QE as the TIs. Nearer the change-over time we will be
contacting any observers who have requested a different CCD from the
one which we will actually be scheduling.

Alistair Walker

Previous Article
Next Article
Table of Contents