Mechanical and Thermal Design of XMM

K. van Katwijk, T. van der Laan & D. Stramaccioni

The XMM spacecraft has a conventional structure and thermal design. Due to the long focal length of the telescopes (7.5 m), the mirrors are far removed from the instruments. On the ground and during the launch, the structure has to maintain the integrity of the whole spacecraft. The thermal control does not make use of onboard software. In orbit, the functions of the structure and the thermal control are mixed. Their global common requirement is to relate and align the set of mirrors at one end of the spacecraft with the set of instruments at the other.

Some parts of the instruments will be kept at cryogenic temperatures, but most of the spacecraft will be kept at about room temperature. It is the task of the thermal control to maintain these diverse requirements by passive and active means. Under inevitably varying thermal conditions, the structure has to stay very 'straight'.