GHRS Instrument Science Report 045

Controlling Background Noise for GHRS Observations: CENSOR 11/92

Ronald L. Gilliland and Lisa E. Walter

Abstract excerpted from the report:

The GHRS has a flight software driven capability of lowering background
noise levels by dropping (and then repeating) any individual step-times
that showed an anti-coincidence event. This GHRS capability may be
invoked by setting the optional parameter of CENSOR to YES (default is
NO). Since the repetition of some step-times will result in a longer
total integration period it is necessary to provide an alignment time
pad for observations using CENSOR. Through analysis of existing data
we show that a time pad of 2% should be adopted for CENSOR
observations. Also supplied is a discussion of how CENSOR works and
what target count rates will have an increased signal to noise as a
result of invoking CENSOR. For best cases the expected gain in S/N
through use of CENSOR is in the 10-20% range.