A joint German–UK–US soft X-ray and extreme ultraviolet (EUV) astronomy satellite; its name is a contraction of Röntgen Satellit and derives from Wilhelm Konrad von Röntgen (1845–1923), the German physicist who discovered X-rays. In the first six months after its launch in 1990 June it carried out an X-ray imaging survey of the entire sky, with a German 0.8-m telescope, and the first-ever survey of the whole sky in the EUV, with the UK’s Wide Field Camera (WFC). Subsequently, the mission was devoted to detailed observations of individual objects. It ceased operation in 1999 February.

http://heasarc.gsfc.nasa.gov/docs/rosat/rosat.html Information page at Goddard Space Flight Center.