MSim simulates the X-ray response of XMM's mirror modules. Therefore, it can also be called a ``ray tracer''. Not only the imaging characteristics of the mirrors, but also losses on the way from the entrance aperture to the detector surfaces are modeled.
Mirror models are approximated as closely as possible to measurements from the Panter facility, in which the hardware was tested. MSim is an important part of the XMM calibration activities, because it is the software module producing the empiric descriptions of such basic quantities as the mirror PSF and the effective area, Ae. These will be used for the highest accuracy instrument calibration instead of actual data arrays, because the multi-dimensional parameter space that would have to be represented by such calibration files is much too large for conventional calibration procedures. MSim, on the other hand, being a highly configurable software module, can take into account many free parameters.
The current version of MSim simulates the following features: