X-Ray Calibration Of The Rosat Position Sensitive Proportional Counter

The prime focal instrument of the ROSAT X-ray telescope, the position sensitive proportio-nal counter (PSPC), has been calibrated extensively with X-rays in the energy range from 0.28 to 1.7 keV. We developed a method to measure the differential spatial non-linearities caused by the digitizing effects of the anode and cathode grids, and the bulging of the thin entrance window, and also the position dependent gain of the counter. From these measurements we derived tables, which are used to correct each single recorded event in position as well as in pulse height. We will present the calibration method and the performance achieved for the PSPC.