Performance of the International Ultraviolet Explorer for spectral imaging

The International Ultraviolet Explorer (IUE) satellite is an astronomical observatory which has obtained more than 25,000 spectral images since its launch in January 1978. A 45 cm f/15 cassegrain telescope feeds two echelle spectrographs of resolution 10,000 with intensified SEC vidicon detectors. Sources are placed for observation using small slews of the spacecraft after positional measurement by an image dissector. Optimum performance requires that the effects of the fluctuating thermal environment be considered in the acquisition and processing of images. The performance of these systems, as evaluated from in-orbit engineering data, are discussed with particular emphasis on the geometrical characteristics.