On-Orbit Dark Background Measurements

R. W. Lyons, W. Baity, E. A. Beaver, R. D. Cohen,
V. T. Junkkarinen, J. B. Linsky, E. I.Rosenblatt
University of California San Diego

Instrument Science Report CAL/FOS-080
August 1992

1. Abstract

We present an analysis of the dark data obtained with the Faint
Ob.ject Spectrograph in the Science Verification proposal SV1316. This
proposal is the science verification continuation of the Orbital
Verification proposal 0V1533. Because of the lindings from that test
(Rosenblatt et al. 1991a) the test procedure was modified slightly to
allow a rnore complete data set to be obtained. The new data, obtained
over a. considerable period of time, sampled a more complete range of
geomagnetic latitude-longitude and allowed us to specify the
dependence of detector background on the geomagnetic latitude more
accurately. No exposures were made inside the boundaries of the South
Atlantic Anomaly. A subset of this data obtained with the burst noise
rejection software enabled was presented in Beaver and Lyons (1992).

We preseut here the form of the background function for the two
detectors and a reasonable approximation for the background count rate
as a function of geomagnetic latitude.