Flight-Like Ground Demonstrations of Precision Maneuvers for Spacecraft Formations—Part II

As part of a multifaceted technology development program for the Terrestrial Planet Finder Interferometer (TPF-I) mission, system-level ground demonstrations of precision formation flying have been performed. These demonstrations were done in the Formation Control Testbed (FCT), a six degree-of-freedom, system-level testbed with flight-like hardware and software. The FCT is described in detail in a companion paper. The formation guidance, navigation/estimation, and control architecture and software used in these demonstrations are also discussed in the companion paper. The demonstrations consisted of synchronized rotations, which couple relative positions and attitudes. For TPF-I, this maneuver will require highest precision formation flying. This paper presents the experimental results for these demonstrations, which are the first major system-level demonstration of precision formation flying control for TPF-I. Multiple synchronized formation rotations were executed with real-time software and centimeterand arc minute-level relative position and attitude performance. The maneuvers occurred over two weeks to show a robust, repeatable capability. The FCT is subject to ongoing development. In particular, these demonstrations had five degrees of freedom: three rotational and two translational. The final translational degree of freedom has since been added. In addition, because terrestrial disturbances in the FCT are more severe than encountered on-orbit, the centimeterand arc minute-level performance of the FCT demonstrations is traced to the TPF-I flight requirements via a simulation-based error budget. We conclude with some directions for further development of formation flying technologies.