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Hubble Space Telescope
GHRS Instrument Science Report 054

GHRS Instrument Science Report 054

"Dark Count Statistics for GHRS Detectors: A Test of Noise Rejection with 
FLYLIM"

Lisa E. Sherbert, Stephen J. Hulbert, Ronald L. Gilliland and
Joseph P. Skapik

Abstract excerpted from the report:

GHRS calibration proposal 4012 was designed to obtain the statistical
data needed to plan an operational strategy for observing faint targets
with the GHRS. The FLYLIM noise rejection strategy is potentially of
most use when one is observing an object so faint that source counts
are well below the level of the detector dark count. In that case it
is possible to reflect multiple-count integrations as instances of
higher-than-average noise without the risk of discarding exposures 
containing genuine signal. The data obtained in proposal 4012 show that
when FLYLIM count rejection is used on the GHRS Detector 2 the dark 
noise is reduced by a factor of four (4) over what is seen well outside
South Atlantic Anomaly (SAA). The rejection of some lines of data 
resulted in an increase in execution time by about 25% over the nominal
exposure time.