SBIR-STTR Award

Station keeping operations of satellites are primarily planned and executed from the ground control centers. With future trends towards operating satellites as part of a larger constellation, both in geostationary orbit (collocation) and lower Earth orbits, the availability of autonomous station keeping will become more critical. This proposal envisions the design of one such innovative autonomous stationkeeping system that will implement the concept of a closed loop Feedback Control using navigational information from both celestial measurements (CM) using Earth-Sun-Polaris angular measurements, as well as GPS measurements. A GPS LQG/LTR Controller will be designed for State Feedback, while a CM PID Controller and H-Infinity Robust Controller will be used for Output Feedback. This design is expected to provide complete autonomy, and will be applicable to both geosynchronous orbits, as well as low Earth orbits. The Phase I research results will be a feasibility study of the proposed design that could eventually be implemented into a usable on-board station keeping system. This proposal is in response to DOD SBIR, 1996, and will be a 6 month offer.

Keywords:
PID CONTROLLER GPS NAVIGATION STATE FEEDBACK OUTPUT FEEDBACK H-INFINITY CONTROLLER GPS LQG/LTR CONT

The maneuver and control for placing satellites into the station orbit and the station keeping operations are primarily planned and executed from the ground control centers. With future trends towards operating satellites as part of a large constellation, both in geostationary orbit and lower earth orbits, the availability of autonomous orbit control/maintenance will become more critical. This proposal envisions one such innovative orbit control/maintenance system that will implement the concept of a closed loop feedback control using GPS LQG/LTR controller and GPS H-infinity robust controller. The pseudorange information for input to the controllers will be obtained from GPS. This design is expected to provide complete autonomy, applicable to both geosynchronous and lower earth orbits. Phase I of this project has been the feasibility study. Feasibility has been established for propsoed autonomous orbit control/station keeping design using the state feedback. It was also demonstrated that the proposed autonomous orbit control is feasible using direct GPS measurement output feedback controller. In Phase II, the design of the proposed autonomous orbit control/maintenance system will be completed, resulting in a prototype design. Phase II will be a 5 man-year effort, over a period of 24 months.