XMM-Newton Science Analysis System: User Guide

5.2 Source extent

The SAS is easy to use for a single dominant point source in the RGS apertures. In this case, the PPS procedure is also successful most of the time. The means also exist to treat more complex source configurations and, with proper care, both multiple point sources and extended sources may be tackled as discussed in below in § 5.9 and § 5.10 respectively. The PPS products are of limited use in these circumstances.

European Space Agency - XMM-Newton Science Operations Centre