ANALYSIS OF FOS ON-ORBIT DETECTOR BACKGROUND
WITH BURST NOISE REJECTION

E. A. Beaver and R. W. Lyons
University of California, San Diego, CASS
Instrument Science Report CAL/Fos-076

April 1992

Abstract

We bave reduced aud analyzed a subset of the FOS detector background
data from proposal SV1316 as a function of the burst noise rejection
parameter REJLIM. For a frame tinie of 0.25 seconds and the lowest
possible rejection setting of 2 or more counts per array readout
(REJLIM=1), the FOS detector background is reduced to around the
0.002c/s/d level (about 20% of the normal backgrouud). As with the
normal background, the REJLIM be.ckground is a functiou of
geoma.gnetic ls.titude. Oornpa.risou of tliis REJLIM detector data
with expectations froin a Poisson distribution generally indicates
tliat a large fraction of the noise has a burst noise origin. The use
of REJLIM should lead to improved S/N for faint object observations
and an improvement of the FOS limiting magnitude
perforrnance. However, for the REJLIM=f~etting, the7fted,Side fraiue
tiiue was not set fast enough to distinquish between a burst uoise or
Poisson character for the detector background. SV1316 with REJLIM~1
should be rerun on the Red side with a 0.05 second or sliorter frame
time.