Abstract—This paper addresses the problem of coordinating multiple spacecraft to fly in tightly controlled formations. The main contribution of the paper is to introduce a coordination architecture that subsumes leader-following, behavioral, and virtual-structure approaches to the multiagent coordination problem. The architecture is illustrated through a detailed application of the ideas to the problem of synthesizing a multiple spacecraft interferometer in deep space. Index Terms—Control architecture, coordinated control, interferometry, spacecraft formation flying. I.

Formation Flying is quickly revolutionizing the way the space community conducts autonomous science missions around the Earth and in space. This technological revolution will provide new, innovative ways for this community to gather scientific information, share this information between space vehicles and the ground, and expedite the Human exploration of space. Once fully matured, this technology will result in swarms of space vehicles flying as a virtual platform and gathering significantly more and better science data than is possible today. Formation flying will be enabled through the development and deployment of spaceborne differential Global Positioning System (GPS) technology and through innovative spacecraft autonomy techniques. This paper provides an overview of the current status of NASA/DoD/Industry/University partnership to bring Formation Flying technology to the forefront as quickly as possible, the hurdles that need to be overcome to achieve the formation flying vision, and the team's approach to transfer this technology to space. It will also describe some of the formation flying testbeds, such as Orion, that are being developed to demonstrate and validate these innovative GPS sensing and formation control technologies.

Abstruct-Formation flying is defined as a set of more than one spacecraft whose states are coupled through a common control law. This paper provides a comprehensive survey of spacecraft formation flying control (FFC), which encompasses design techniques and stability results for these coupled-state control laws. We divide the FFC literature into five FFC architec-tures: (i) Multiple-Input Multiple-Output, in which the formation is treated as a single multiple-input, multiple-output plant, (ii) Leader/Follower, in which individual spacecraft controllers are connected hierarchically, (iii) Virtual Structure, in which spacecraft are treated as rigid bodies embedded in an overall virtual rigid body, (iv) Cyclic, in which individual spacecraft controllers are connected non-hierarchically, and (v) Behavioral, in which multiple controllers for achieving different (and possibly competing) objectives are combined. This survey significantly extends an overview of the FFC literature provided by Lawton, which discussed the L/F, Virtual Structure and Behavioral architectures. We also include a brief history of the formation flying literature, and discuss connections between spacecraft FFC and other multi-vehicle control problems in the robotics, UAV, underwater vehicle and Automated Highway System literatures. I.

apertures formed by formation fl ying spacecraft provide desirable characteristics compared to earth based or centralized apertures located on one structure. Also, the ability to easily form and reconfigure very long baselines for uniform and dense u-v (observing) plane coverage [8, 9] provides a clear advantage over traditional systems. However, there are major technical challenges in achieving the aperture coordination, control, and monitoring of these distributed vehicles that will be necessary to achieve the stringent payload pointing requirements [6, 7]. In addition, thefl eet control design must be done with careful consideration of the onboard computation, inter-vehicle communication, and power requirements for the formationfl ying spacecraft. Thus a systems-level approach is essential, allowing explicit inclusion of the hardware limitations (power, mass, computation) in the theoretical analysis of the various multi-level control architectures

The recent addition of autonomous formation flying spacecraft to the world’s satellite fleet provides new motivation to study feedback control techniques. In this thesis, we develop nonlinear orbit control laws for use in spacecraft orbital maneuvers, and spacecraft formation flying. We apply these new control laws to a number of sample maneuvers, including formation establishment and formation keeping maneuvers for NASA-Goddard’s Leonardo-BRDF formation, and coupled orbit, and attitude maneuvers for HokieSat, a spacecraft designed, and built by students at Virginia Tech to fly in the Ionospheric Observation Nanosatellite Formation (ION-F). To provide target orbit states for feedback control, we develop and apply an algorithm to calculate a formation master orbit representing the geometric center of the formation. We also define a new technique for choosing orbital element feedback gains which appropriately scales the gains for orbit maintenance, and provides an excellent starting point for gain optimization. The orbital element feedback control law, augmented by mean motion control, and applied with appropriate gains, forces asymptotic convergence to a spacecraft target orbit, for a large variety of spacecraft maneuvers. Acknowledgments