GHRS Instrument Science Report 077 "Anomalies in the Calibration of GHRS Grating G270M" Melissa A. McGrath Oct 17, 1996 Abstract Two anomalies in the calibration of the GHRS G270M grating are reviewed. The pre-COSTAR, in-flight sensitivity calibration used in the pipeline processing between Nov. 11, 1991 and April 14, 1994 is erroneous shortward of 2300. The pre-COSTAR vignetting correction for grating G270M is inadequate shortward of 2300, and the post-COSTAR vignetting correction shortward of about 2150 is not handled properly by calhrs. The vignetting correction calibration problem is symptomatic of the underlying problem, which is that the y-deflection has not actually been measured below 2300.
