A joint US–German–UK satellite launched in 1990 to study cosmic sources of X-rays and extreme-ultraviolet (EUV) wavelengths, named after German physicist Wilhelm Röntgen, the discoverer of X-rays. After more than 9000 observations of objects including comets, quasars, black holes, clusters of galaxies, and supernovae, the satellite was finally switched off on 12 February 1999.

ROSAT was designed to produce the first all-sky fully imaging surveys in the X-ray and extreme ultraviolet parts of the spectrum. The satellite used a German X-ray telescope developed under the leadership of the Max Planck Institute, and the Wide-Field Camera (extreme-ultraviolet telescope) constructed by a UK team led by the University of Leicester and funded by the UK's Particle Physics and Astronomy Research Council (PPARC). The USA provided an additional X-ray camera and the launch vehicle, and the main spacecraft and mission operations were funded by Germany.

http://astroe.gsfc.nasa.gov/docs/rosat/rosgof.html Profiles the nine-year Röntgen Satellite (ROSAT) mission and describes the spacecraft and its science payload. There is extensive technical documentation, including the ROSAT users' handbook, access to data from the mission, and a very good image gallery.