Relative Orbit Control Design for the PRISMA Formation Flying Mission

Abstract

Time has come for the first European fully autonomous close-range formation flying demonstration in low Earth orbit. The PRISMA technology demonstration mission, originating from an initiative of the Swedish National Space Board and the Swedish Space Corporation, is currently in its development phase and will realize formation flying and rendezvous experiments involving two spacecraft at an altitude of 700km. In the frame of the German Aerospace Center’s contribution to PRISMA, this study addresses the GPS-based guidance, navigation and control (GNC) on-board functionalities for the maintenance of a robust and safe relative motion between two spacecraft with typical accuracies of a few tenths of meters and minimum thrusters usage. After an introduction of the GNC concept based on real-time GPS measurements filtering, relative orbital elements parameterization, and impulsive orbit control, emphasis is given to real world simulations of the system including the modeling of sensors and actuators. Finally, the paper derives realistic estimates of the expected relative orbit control performances and their dependencies on the accuracy of the GPS data filtering and the characteristics of the propulsion system.