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 were the prime focal plane instruments on board the X-ray astronomy satellite ROSAT. ROSAT was launched on June 1, 1990 and operated very efficiently. The authors report the orbit performance of the PSPC. Apart from its good energy and position resolution the detector had a very high-charged particle background rejection efficiency of 99.8%. The gas gain of the detector was very stable. Short-time variations due to thermal variations over one orbit were less than 1%. The long-term drift over one month was 0.5%