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Hubble Space Telescope
GHRS Instrument Science Report 042

GHRS Instrument Science Report  042

"Trends in GHRS Far-UV Sensitivity"  10/92

Ronald L. Gilliland and Lisa E. Walter

Abstract excerpted from the report:

The GHRS has an ongoing absolute sensitivity monitoring program that now has a
total baseline of over 1.5 years. The 2.0 arcsec LSA is used to observe a
standard star every few months at five wavelengths: 1200A, 1500A, 2000A,
2500A, and 3000A. A trend analysis is consistent with long-term stability at
all wavelengths. In particular the far UV (1200A) sensitivity relative to the 
near UV (mean of 2500A and 3000A measures) does not show any significant trend
with time. The GHRS data suggests that the OTA far UV response is not 
degrading with time; independent measurements on two different stars yield
formal trends of -2.8% per year and +0.7% per year for the far to near UV
response.