The objective of this dissertation is to develop a precision rendezvous methodology for Earth orbiting spacecraft utilizing the Global Positioning System (GPS). A GPS receiver is placed on each space vehicle and a communication link is used to pass GPS measurements from the target to the chaser spacecraft. The integrated navigation and guidance system resides on the chaser vehicle. The fundamental component of the measurement processing navigation system is a real-time recursive extended Kalman filter (EKF). The navigation system provides absolute and relative position and velocity estimates that are used by the on-board guidance for computing rendezvous maneuvers without ground support. To achieve very precise relative navigation, the filter processes double-difference carrier phase measurements. The unavoidable double-difference integer ambiguity is part of the filter state and is treated as a real number.; The Global Simulation Systems (GSS) STR4760 GPS signal generator was used to perform open-loop simulations to evaluate the relative navigation filter performance in conjunction with a commercial, user programmable GPS receiver that was extensively modified for space applications. Open-loop implies that no on-board targeted rendezvous maneuvers are executed. The open-loop simulation investigations show that a 5 cm or less relative positioning accuracy and about a 1 mm/s relative velocity estimation accuracy are achievable. With these highly accurate relative navigation results, the notion of autonomous space rendezvous becomes plausible.; One of the key contributions of this research involves the development of a hardware-in-the loop (HWIL) GPS test facility, which is capable of performing active closed-loop scenarios in real-time mode with actual GPS signal processing hardware. The GSS STR4760 is a closed-loop simulation system capable with the GSS STR4762 Remote Control option. The HWIL GPS test facility was constructed and configured to evaluate the newly developed relative navigation algorithms integrated with on-board targeting from real-time navigation data. This is the first time this type of hardware for closed-loop spacecraft rendezvous experiments has been reported.
展开▼
