Mission Operations
Orbit
A Halo orbit around the second Lagrangian point of the Sun-Earth system (L2) provides optimal conditions. The chosen orbit can be reached in about one month with an almost full-year launch window. L2 provides the necessary low gravity-gradient environment for economical formation flying, long observing windows and optimal cooling for the instruments.
Launcher
XEUS will consist of formation flying Mirror and Detector spacecraft (MSC and DSC). The MSC contains the X-ray optics and the DSC the prime focal plane instruments. The instruments will be kept at the focus of the X-ray optics (one at a time) using the concept of formation flying. The two spacecraft will be launched together in a single stack on an Ariane 5 ECA. The MSC, with a 4.2 m diameter mirror fits in the 4.57 m diameter of the Ariane 5 ECA fairing. The inner diameter of the mirror is compatible with an 1194H adapter. The DSC will be mounted on the top of the MSC. With non-deployable baffles, the spacecraft stack fits in the length of a medium fairing. In this configuration the launcher can place both spacecraft at L2 using a direct launch and with a total mass of 6.5 tonnes.