The Attitude and Orbit Control of XMM

A. Elfving

Attitude and orbit control of the XMM spacecraft relies on two subsystems on-board: the Attitude and Orbit Control Subsystem (AOCS) and the Reaction Control Subsystem (RCS). Together they must provide:

• stable Sun-pointing after the spacecraft's separation from the launcher and during solar-array deployment
• increase the spacecraft's perigee altitude by means of a chemical propulsion delta-V of about 210 m/s
• provide undisturbed, high-accuracy, three-axis pointing during scientific observations lasting up to 40 h
• slew the spacecraft between observations, and before and after perigee
• ensure that the Sun remains more than 15 deg away from the telescope at all times.