copyright European Space Agency
The XMM- Newton satellite was launched by the European Space Agency late in 1999. XMM-Newton is currently the largest X-ray (0.2-12keV) telescope in operation. Three co-aligned telescopes feed two EPIC MOS (Turner et al.2001, A&A,365,L27) and one EPIC pn (Strueder et al.2001 A&A, 365,L18) cameras. Two reflection grating arrays deflect about half of the X-ray photons from the EPIC MOS camera towards two Reflection Grating Spectrometers (RGS; den Herder et al. 2001, A&A, 365, L7). An Optical Monitor (OM; Mason et al. 2001), providing UV and optical images of a fraction of the field of view covered by the EPIC cameras down to magnitude 21, complement the X-ray instrumentation. One of the remarkable properties offered by the X-ray telescopes onboard XMM-Newton is a large field of view of 30 arcmin diameter with only weakly degraded image point-spread function and low vignetting even at large off-axis angles. Accordingly, a high number of sources are serendipitously discovered around the main target of the observation, which accumulate to make an X-ray survey with an unprecedented combination of sensivity and area covered.