GHRS Instrument Science Report 055 "Line Spread Functions for GHRS Spectra with the LSA (Pre-COSTAR) Ronald L. Gilliland and Stephen J. Hulbert Abstract excerpted from the report: The spherically aberrated point spread function of the HST provides input to the 2.0" LSA that is characterized by a sharp core and broad wings. The extended PSF wings contribute to a significant resolution degradation for spectra acquired through the LSA. The 0.25" SSA is matched in size to the spectroscopic resolution element; spectra taken in the SSA suffer a loss of throughput, but no significant resolution degradation. Through comparing spectra of a sharp-lined star acquired through both the LSA and SSA it is possible to derive the added line spread function (LSF) blurring of the LSA relative to the SSA. We report on empirical determination of the LSA spectral resolution degradation for three different wavelengths and four spectral elements of the GHRS.
