A Lagrangian heuristic for satellite range scheduling with resource constraints

The task of scheduling communications between satellites and ground control stations is getting more and more critical since an increasing number of satellites must be controlled by a small set of stations. In such a congested scenario, the current practice, in which experts build hand-made schedules, often leaves a large number of communication requests unserved. We report on our experience in the design of an optimization-based support tool at the European Space Agency. We propose a tight time-indexed formulation of the problem able to include several complex technological constraints. A non-standard Lagrangian heuristic is then devised which provides near-optimal solutions of a set of largescale test problems arising in the forthcoming GALILEO constellation. The heuristic shows numerical stability and robustness adequate for practical implementation. The resulting tool is used by the Italian reference operator for GALILEO system management and is currently under testing at the European Space Agency.