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CCD Controllers: The Next Generation (1Sep92)
(from KPNO, NOAO Newsletter No. 31, 1 September 1992)

The KPNO CCD controllers are now 12 years old, and for the past few
years CTIO and KPNO have been working collaboratively to develop the
"next generation" controllers. The first on- the-telescope tests of the
new system at Kitt Peak were carried out on the 2.1-m telescope on 8
June. We expect to replace all our current controllers with the new
ones over the next year. The user interface will remain that of ICE for
the present.

The advantages of the new system over the old include high speed
readouts, improved dynamic range, and quad readout. Astronomers will
immediately realize a factor of 2 decrease in the time spent reading
out the chip. In addition, many of our CCDs have low (<  5 electrons)
read-noise and very deep full-well capacities (>  200,000 electrons).
With the current controllers we are limited to 15-bit A/D converters,
and hence must set the gain either to under-sample the read-noise or to
give up dynamic range; with the "real" 16-bit A/D converters of the new
controllers, we gain a factor of 2 in dynamic range for the same
read-noise sampling.  Finally, quad readout (the ability to
simultaneously read out through four amplifiers) will yield another
factor of 4 speed-up in the time it takes to read out a single CCD with
four working amplifiers; it is also crucial for effective operation of
our planned "mini-mosaic" of four 2048 x 2048 CCDs. With modern
electronics we can achieve these gains at low cost, with low power
dissipation, and use inexpensive and reliable fiber-optic links.

This first version of the KPNO "Hybrid ARray CONtroller," dubbed the
"HARCON," is based very closely on the CTIO ARCON, but adapted to
interface to the KPNO analog electronics. It uses a VME-based
Transputer plug-in board to talk to a Sun workstation, and a high-
speed fiber-optic link for the data and command path to the controller
electronics located at the telescope. The present control software has
been developed exclusively at CTIO and runs unmodified on the KPNO Sun
workstations.

The picture below was obtained with the T1KA CCD and HARCON on the
2.1-m telescope and shows a narrowband image of the planetary nebula
Abell 72.  Readout noise and data integrity appear to be uncompromised
with the HARCON when compared with the classic KPNO controllers.

		       [figure not included]

Andy Rudeen, George Jacoby

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