Implication and usefulness of spacecraft servicing at the ISS using the pilot case of the large X-ray facility XEUS

The X-Ray Rvolving Universe Spectroscopy mission XEUS aims to place a permanent X-ray observatory in space with a telescope aperture equivalent to the largest ground based optical telescopes currently built to date. XEUS foresees a large mirror spacecraft (MSC), whose diameter of some 10 m and mass of some 25 t prevent it from being launched in one piece. Therefore it is designed to be assembled in- orbit on board the ISS, with a circular core mirror (MSC1) and eight mirror sectors attached to it, to form the final MSC2. The MSC2 assembly sequence is described, addressing logistics, robotics, EVA, other ISS resources and operations aspects. The assembly concept relies on the use of robotic arms of the Shuttle (SRMS) as well as both ISS robotic arms (SSRMS and ERA) and makes use of various remotely controlled attach mechanisms. EVA support is reduced to some final deployment and verification.