EXOSAT: The European X-ray observatory satellite

A detailed study of known X-ray sources is planned. The precise location of sources is determined with an accuracy of about ten seconds of arc using the two imaging telescopes and the medium energy experiment in conjunction with the lunar occultation mode (to an accuracy of about two seconds of arc). Diffuse extended sources such as supernova remnants are mapped, and sources within nearby galaxies and galaxies within clusters are resolved using the imaging telescopes. Broad band spectroscopy is performed, i.e., the X-ray "color' of sources are determined using the complete payload and high precision spectroscopy using transmission gratings with the imaging telescopes. The time variability of sources over time scales ranging from milliseconds to days is studied. Bursters, transients, pulsars, eclipsing binaries, and active galaxies are observed.