GHRS Instrument Science Report 071

"Stability of the GHRS Sensitivity During Cycle 4"

Claus Leitherer and Lisa E. Sherbert
June 1995

Abstract

The sensitivity of the GHRS on Side 1 and Side 2 was monitored
approximately every 3 months during Cycle 4. The measurements were done
with the ultraviolet flux standard BD+28D4211. No significant time
dependence was found for wavelengths > 1200 A on both sides; any
accumulated sensitivity changes during Cycle 4 do not exceed about 2%,
although the data indicate a decline rate per year of this magnitude.
Below 1200 A the sensitivity decreases with time. In April 1995 the
sensitivity at 1140 A was 10% lower than measured in April 1994.