FOS STABJLITY AFTER SHORT HV 0FF

E.A. Beaver, R. D. Cohen, D.S. Tudhope and W.A. Baity
Univer.sity of California, San Diego

Instrument Science Report CAL/FOS-057
February 1989

Abstract

A full 30-minute delay is currently specified after every HV an, even
when the 11V has only beeu off for a few minutes, such as in an SAA
Passage. If this delay could be reduced to 10 minutes, we would
potentially gain over 2 hours observation time per day. Ta study this
matter we bave searched the FOS engineering data base, but there was
little usable data, and it was all at +2O~C, with HV offs of 30
iniriutes or marc. Tests were made at SAIC an spare digicons which
slrnw ac.ceptable stability at +200C after 2-3 minutes. These tests
also show lack of acceptable stability until 5-30 minutes at 00C, with
a reasonable extrapolation to even langer times at -100C, the
operational temperature. A test at LMSC only confirmed the SAIC
measurements at +200C, at 10 minutes after HV an. lt is strongly
recommended that further tests be run at -100C at SAIC.