Real Time GPS Attitude Determination for LEO Micro-Satellite

摘要

This paper presents the theory and results of a GPS-based attitude determination instrument for LEO Micro-Satellite Project. Our purpose is to design a system, which is both ro-bust and accurate. A demonstration system is developed and tested. Ashtech G12 single frequency receivers are used in this system, providing the required carrier phase observation and ephemeris data. This system uses the interferometric processing of the GPS L1 signals to determine the attitude Euler angle rotations. On the basis of the carrier phase observation model, the non-linear equation could be solved iteratively. After coordinate system transformation, we achieve the Euler angle in body frame. This system's attitude updates is an independent measurement, so that it could work indi-vidually or be incorporated with some other attitude determination systems easily. Utilizing the spinning property of this LEO satellite, the integer ambiguity is resolved by an instantaneous method, i.e. solution for the GPS integrated carrier Doppler wavelength ambiguities (integer ambiguity) doesn't depend on the observation over a long time. Double-check is provided. In this way, further improvement of the robustness in this realization is achieved because the system could be quickly reset and initialized at any time. This instantaneous property, together with the cycle slip detection routine, renders the system resistant to cycle slip. Results are presented using actual observation data from GPS LI signal proving its accuracy and stability. This system could be used in LEO satellite application, as well as other vehicles.