Formation Flying Spacecraft

Many future space missions, such as space-based radar, earth mapping, and inter-ferometry, will require formation flying of multiple spacecraft to achieve their very advanced science objectives. While formation flying offers many performance and op-erational advantages, there are several challenges that must be addressed, including navigation, control, autonomy, distributed data management, efficient inter-vehicle communication, and robustness. One of the key issues with formation flying of large fleets is selecting the overall system architecture, because it drives the distribution of the various algorithms and the extent to which data must be transmitted. These challenges are particularly evident with the relative navigation. While carrier-phase differential GPS can be used as a highly accurate sensor for LEO for-mations, it is not sufficient as the sole sensor for missions beyond LEO. If local ranges and range rates are used to augment or replace the GPS measurements, precise es-timation can continue into MEO and beyond. However these new measurements complicate the estimator decentralization by coupling the vehicles ’ state estimates