GPS Navigation System For Challenging Close-Proximity Formation-Flight

Abstract

The PRISMA mission has demonstrated the benefits of employing on-board GPS-based relative navigation for precise formation-flying, allowing the design of lowcost, reliable and accurate sensors essential for precise formation control and mission safety. GPS-based navigation poses some requirements in terms of visibility of the GPS constellation, which are necessary to ensure ultimate performance and which can however be hard to satisfy by some of the upcoming distributed spacecraft systems aiming at embarking such a GPS navigation system. In the paper, the architecture of the PRISMA GPS navigation system is revisited, in order to better support challenging formation-flying missions with non-optimal visibility conditions, such as inertially pointing virtual telescopes or on-orbit servicing missions. The new design foresees the simultaneous usage of a second GPS receiver on each spacecraft to enforce omnidirectional tracking capability, able to provide a large amount of GPS measurements and to achieve real-time relative navigation performance better than 10 cm 3D rms in any situation.