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Hubble Space Telescope
GHRS Instrument Science Report 080

GHRS Instrument Science Report 080

"Offsets in Wavelength Between the Large and Small Science Apertures
of the GHRS"

A. Schultz, D. Soderblom, S. Hulbert, and L. Sherbert

March 7, 1997


The wavelength shifts (offsets) between the GHRS LSA and SSA have been
determined from the measured pixel shift for stars observed in both
apertures. HD155763 (Zeta Dra) was observed with the first order
gratings, while HD141556 (Chi Lupi) was observed with Ech-A and Ech-B,
both as GHRS calibration proposal 6213. The target stars were first
centered and observed in the LSA followed by slewing the telescope to
position the target in the SSA. To eliminate movement of the carrousel
between observations, No SSA ACQ/PEAKUPs were performed to center the
targets in the SSA. This report summaries the observations, data
reductions, and wavelength offset calculations. We find values for
these offsets that are significantly different from the values
determined in SV, and with better internal precision. Table 9 at the
end summarizes these new values.