FORMATION KEEPING AND MANEUVERING FOR ASTRONOMICAL, DUAL SPACECRAFT FORMATION FLYING MISSIONS

Typical astronomical satellite missions maintain inertial pointing over extended periods. In the case of a distributed observatory formed by an optical assembly and a detector assembly flying in formation, the challenge is to keep the formation aligned inertially to within tight tolerances, while counteracting the natural tendency to formation disgregation. We investigate strategies for acquisition, keeping and reconfiguration of the formation to satisfy an observational schedule. Simulations are carried out accounting for all relevant forces and using Lambert targeting and differential corrections for coarse and fine formation acquisition and reconfiguration. Formation keeping is simulated based on a thrust profile derived from a simple theorem of relative motion. Simulations are performed simply as a forward modelling problem without closed loop control of the chaser. Thruster and orbital restitution uncertainties are modelled. A set of X-ray sources has been adopted from the XMM mission as observation targets for implementation of the observational schedule subject to several viewing constraints. The resulting thrust and fuel consumption profiles are provided corresponding to different operational strategies, together with their evaluation of their effectiveness.