EXOSAT- Present Status and Future Prospects

The design and operation of the ESA Exosat orbiting X-ray observatory (launched in May 1983) are reviewed, and some preliminary results are summarized. The value of X-ray observations for investigating hot sources assumed to be driven by accretion into neutron stars is indicated; the low-energy imaging telescopes, medium -energy experiment, and gas scintillation counter making up the Exosat payload are briefly characterized and illustrated with drawings and tables of instrument parameters; the advantages of real- time control via the continuous telemetry link and of orbital- velocity changes to permit lunar-occultation position determinations are discussed; and sample spectra and light curves are shown.