Subject: GRIM II Exposure Timing and Non-Linearity

From: Alan Watson

Submitted: Mon, 8 Jul 1996 11:36:04 -0600

Message number: 20 (previous: 19, next: 21 up: Index)

We have written a report on GRIM II exposure timing and non-linearity.
The gist of our report is:

    (a) The exposure time is currently OPENTIME + 0.901 +/- 0.006
    seconds and is about 0.2 seconds less than the requested time.
    It appears that the exposure timing changed sometime between
    October 1994 and April 1996, but we do not know when.

    (b) The corrections for non-linearity are well-determined and
    can be as large as 10%. We have written an IRAF task to
    perform the correction.

    (c) It is fairly easy to expose past the working range of
    about 28000 DN because of the reset-read-read mode in which
    the array operates. Uncorrectable saturation can occur at
    levels as low as 13000 DN. We present a graph of the maximum
    safe exposure as a function of exposure time.

The report can be obtained from

    ftp://oldp.nmsu.edu/pub/alan/grim/lin.ps.Z.

We welcome comments.

Alan Watson (awatson@nmsu.edu)
Nancy Chanover (nchanove@nmsu.edu)
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