An Adaptive Approach for Impulsive Formation Maintenance Relevant to Distributed SAR Missions

This paper proposes an approach for impulsive formation maintenance tailored to distributed synthetic aperture radar, i.e., a spaceborne system composed by several antennas working together to provide enhanced remote sensing capabilities. The analyzed configuration is designed to guarantee the presence of a safety tube surrounding each satellite as the dynamics evolve. Formation requirements are related to general constraints on the acceptable along-track and radial/cross-track separations. The paper introduces an adaptive maintenance logic which fulfills these constraints. Specifically, the formation is adaptively redesigned around the chief every time geometry constraints are violated by means of a procedure developed by the authors in previous works and based on relative orbit parameters. Once these parameters are defined, the optimal impulsive burns required for orbit transfer are computed using state-of-the-art approaches. Performance in terms of delta-v and maneuver frequency is analyzed for a two-spacecraft formation exploiting a simulation environment based on MATLAB and GMAT. In ideal conditions, it is shown that maintenance costs are limited, while close proximity requires fine sensitivity on the applied impulses. A first assessment of the impact of relative navigation and maneuvering execution errors indicates that they play an important role in defining the overall control effort.