Inflight performance of the position sensitive proportional counter on board the X-ray astronomy satellite Rosat

Two redundant position sensitive proportional counters (PSPC) operating in the energy range from 0.1 to 2.4 keV are the prime focal plane instruments on board the X-ray astronomy satellite Rosat, Rosat was launched on June 1, 1990 and has operated highly efficiently since then. The authors report on the in-orbit performance of the PSPC. Apart from its food energy and position resolution ( delta E/E=41% and 230 mu m full width at half maximum at 1 keV, respectively) the detector has a very high charged particle background rejection efficiency of 99.8%. The gas gain of the detector is very stable. Short-time variations due to thermal variations over one orbit are less than 1%. The long-term drift over one month is 0.5%.<>