A German X-ray satellite developed through a cooperative program with the United States and the United Kingdom. The satellite, launched by a Delta rocket (Cape Canaveral) on June 1, 1990, operated until February 12, 1999. ROSAT consisted of two telescopes performing in the → soft X-ray (0.1-2.4 keV) and → extreme ultraviolet (EUV) (006-0.2 keV) ranges. It carried out the first → all-sky surveys with imaging X-ray and EUV telescopes leading to the discovery of 125,000 X-ray and 479 EUV sources. In addition the diffuse Galactic X-ray emission was mapped with unprecedented angular resolution (≤ 1 arcmin). Most of the mission time was devoted to pointed observations at selected targets. ROSAT imaged everything from nearby asteroids and comets to distant quasars during its 8-year mission. The main ROSAT data centers were and are at the Max Planck Institute for Extraterrestrial Physics in Garching (X-rays) and at the University of Leicester (EUV) with mirror sites at the Goddard Space Flight Center and other research institutes.