The SXRP flight model will be calibrated at Lawrence Livermore National Laboratory, with both a polarized and unpolarized X-ray source, prior to being shipped to Moscow. Individual detectors are also calibrated at Columbia University before integration with SXRP.
In-flight, each detector has, imbedded in the titanium strong back of the beryllium window, a small Fe-55 radioactive source. These sources were produced with an activity of 10 microCuries each in the autumn of 1992; by the autumn of 1995 the sources will have decayed and be producing a count rate of approximately 1 count per second in each detector. The 5.9 keV line of Fe-55 allows the gains of the detectors to be monitored throughout the flight.
SXRP has four on-board Fe-55 sources placed in the window of the detectors. Each source was approximately 10 microCuries in August 1992. The sources are imbedded in the detectors and emit no radiation detectable outside the SXRP.