XEUS

Construction of XEUS 2 on the Space Station uses the European Robotic Arm to attach new mirrors.

The size of the first version of the telescope, XEUS 1, is limited by the capacity of the big Ariane-5 launcher. The mirror and detector spacecraft are expected to be mated for the launch, and to separate in space. XEUS is expected to operate 600 kilometres above the Earth, in a so-called fellow-traveller orbit directly above the Space Station. But the X-ray mission remains completely independent of the Space Station until, after perhaps four years, the time comes to enlarge XEUS 1 to XEUS 2.

To obtain the 5-fold mirror growth, XEUS uses its thrusters to descend to the Space Station, which flies at 350 to 400 kilometres altitude. The mirror spacecraft docks in a transfer-vehicle port on the Russian segment of the Space Station. The US Space Shuttle or the European Automated Transfer Vehicle (ATV) has already delivered the eight additional mirror sectors to the Space Station. A robotic arm from the Space Station then places the sectors one-by-one around XEUS 1 as it grows into XEUS 2. Space-walking astronauts finish the job. The mirror spacecraft then returns to its 600-kilometre orbit.