Spaceborne Autonomous Relative Control System for Dual Satellite Formations

Autonomous formation flight is a technical challenge of great interest for many scientific missions. Among other applications, the design of synthetic apertures is a promising benefit of using distributed spacecraft. Even if numerous studies exist in the literature, the formation flying concepts and applications were until now rather theoretical. The TanDEM-X Autonomous Formation Flying system presented in this paper will be implemented in the upcoming TanDEM-X mission and contributes as such to increase the readiness level of this technology. The paper focuses on the design of a guidance, navigation, and control system enabling the autonomous relative control of two spacecraft flying on near-circular orbits. Emphasis is given to the practical implementation within an onboard embedded computer, which requires a simple, resource-sparing, and robust design of the system. Therefore, the algorithms are tailored to minimize the usage of onboard resources and to allow the harmonious integration of the relative control system within the space segment. The validation of TanDEM-X Autonomous Formation Flying performed using a hardware-in-the-loop testbed shows that control performance at the meter level is expected.