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Hubble Space Telescope
GHRS Instrument Science Report 034

GHRS Instrument Science Report 034 

"GHRS Photocathode Flat-Field Maps"  July 1991

By: Ronald L. Gilliland

Abstract excerpted from the report:

The first stage of the GHRS detection system consists of UV light sensitive
photocathodes. Output from these two-dimensional photocathodes, in the
form of an electron based image is ultimately detected using a one-dimensional
digicon-diode array. A narrow slice from the photocathode (containing
the illuminated spectrum in normal operation) is projected onto the digicon
array via magnetic deflection control. Variations of sensitivity across
the photocathodes (granularity) exist in several guises and are discussed
in the GHRS Instrument Handbook. A general 2-D flat-field response map,
sufficient for calibration is not available. The maps described in this
report are sufficient for planning purposes of locating the position of
particularly large sensitivity variations. It is the purpose of this report
to document binary-format photocathode maps being made available through
STEIS.