The ROSAT satellite was launched on July 1, 1990 into a circular orbit with an inclination of and an altitude of 580 km. The last observation was made on December 18, 1998 and the official end of the ROSAT mission is February 12, 1999.
The larger of the two telescopes on board ROSAT is a grazing incidence X-ray telescope (XRT) consisting of four nested Wolter type I mirrors. The X-ray imaging telescope (XRT) was used in combination with either the Position Sensitive Proportional Counter (PSPC) or the High Resolution Imager (HRI) as focal detector.
Two observation modes, pointed observation and survey observation, were possible. In pointed observation the instrument's optical axis remained nominally fixed relative to the observation target within the observation interval. In survey observation mode, the optical axis (as unit vector) describes nominally circles in a plane perpendicular to the direction Earth-Sun.
The ROSAT All-Sky Survey (RASS) was performed with the PSPC detector. ROSAT carried the Wide Field Camera (WFC), a third imaging instrument with a separate extreme ultraviolet imaging telescope (XUV) co-aligned with the XRT. This telescope is comprised of a nest of three grazing incidence Wolter-Schwarzschild type I mirrors. For further details, see the instrument description in Trümper (1990, 1991) and the instrument specific papers.
Copyright The European Southern Observatory (ESO)