The X-ray Multi-Mirror (XMM) Telescope was launched by ESA on December 10th, 1999 and carries two distinct types of telescope: three Wolter type-1 X-ray telescopes, with different X-ray detectors in their foci, and a 30-cm optical/UV telescope with a microchannel-plate pre-amplified CCD detector in its focal plane. The Optical Monitor can provide spectral resolution by the use of broad- and narrow-band filters contained within a filter wheel, plus there are also two grisms in the filter wheel for low resolution spectroscopy. The spatial pixel size in normal operation is 1 arc second and the limiting sensitivity is B=24 for a star viewed with the detector in unfiltered light.

Real time tracking for XMM