XMM-Newton Users Handbook Count rate conversion from other X-ray satellite missions

For the conversion of count rates from other X-ray satellites to count rates expected for the different XMM-Newton detectors, we recommend the use of the PIMMS software from NASA's HEASARC . HEASARC updates XMM-Newton response matrices in PIMMS regularly before each AO, using the publicly available SAS.

European Space Agency - XMM-Newton Science Operations Centre