The world's most powerful observatory for X-ray astronomy, the European Space Agency's XMM satellite, set off into space from Kourou, French Guiana, at 15:32 Paris time on 10 December 1999. The mighty Ariane 5 launcher, making its very first commercial launch, hurled the 3.9-tonne spacecraft into a far-ranging orbit.

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).