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Hubble Space Telescope
GHRS Instrument Science Report 071

GHRS Instrument Science Report 071

"Stability of the GHRS Sensitivity During Cycle 4"

Claus Leitherer and Lisa E. Sherbert
June 1995


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.