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.
