Ariane 5 is an ESA programme for which ESA delegated management responsibility to CNES.
Launch operations are managed by Arianespace at the ELA-3 launch site at the Guiana Space Centre, Europe's space port (French Guiana).
The scientific objectives of the XMM mission, for high-through put X-ray spectroscopy, call for a powerfull imaging instrument with the largest possible collecting area, for high-quality spectral measurements of faint sources down to 2x10 -15 erg/cm2/s, together with fast low -and medium- resolution spectroscopy of brighter objects.
An assembly of 51 mirrors, carefully sized, formed and nested one inside another, makes the most sensitive X-ray telescope ever built. XMM will carry three identical telescopes of this kind.
This astrophysics mission is a "Cornerstone" in ESA's long-term Space Science Programme "Horizon-2000" and the launch took place on 10 of december 1999.