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Array Controller Update (1Sep92)
(from CTIO, NOAO Newsletter No. 31, 1 September 1992)

Another major milestone has been passed in the process of building the
Arcon, our new array controller (see Newsletter No. 29, page 15). For
tests made at the Schmidt telescope in early June, the prototype
controller (Arcon2.1) was equipped with a quad-channel video card,
which simultaneously reads all four amplifiers of a Thomson CCD. The
signals are digitized by four ADCs operating in parallel and then
passed to the Sun computer via a single optical fiber link.

The Arcon tests were a complete success. The 1024 x 1024 CCD could be
read out in 11 seconds. Unscrambling the quad image, presently done as
an IRAF task, takes a few more seconds.  Meanwhile, the picture can be
viewed on the Real Time Display in de-scrambled form. Each CCD output
amplifier has a slightly different bias level and gain calibration.
These differences are currently visible on the real time display, but
standard reduction procedures produce final pictures indistinguishable
from those obtained when the CCD is read out through a single
amplifier. Future releases of the display software will automatically
adjust bias and gain to minimize visual differences. Crosstalk or other
undesirable effects were not detected.

With the success of this test the project to make a prototype
controller has been declared finished. We are now building production
controllers (Series Arcon3) as rapidly as possible. We expect the first
of these controllers to appear in routine use on Tololo before the end
of this year. Resources permitting, the transition to Arcon controllers
on Cerro Tololo should largely be completed by the end of calendar year
1993.

A related project at KPNO has resulted in the construction of "HARCON,"
a Hybrid of the Arcon and the present KPNO controllers. These tests
were also successful and are discussed elsewhere in this Newsletter.

Alistair Walker, Roger Smith,
Dan Smith, Tom Ingerson

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