Orbit determination using the geomagnetic field measurement via the unscented kalman filter

Orbit determination of spacecraft using only magnetometer measurements via the unscented Kalman filter (UKF) is presented. An algorithm was formulated by adopting the UKF and an adequate dynamic model developed for processing geomagnetic field measurements. The paper consists of the analysis of force and estimation models, the dependency of position accuracy on orbit type, and measurement errors, as well as a comparison of the UKF and the extended Kalman filter (EKF). Finally, the developed algorithm used actual magnetometer flight data from the Magnetic Field Satellite (MAGSAT). The results obtained from the MAGSAT data demonstrate that the achieved position error was approximately 2 km. The UKF performs similar to the EKF in position accuracy for a sampling interval of less than 20 s. In contrast, for a sampling interval of 40 s, the EKF yields lower position accuracy than the UKF. In particular, the decomposed position errors are not biased because the UKF is not affected by linearization of the measurement function. This improvement makes the magnetometer-based orbit determination method more robust and reliable as a real-time orbit determination system for small satellites that require moderate position accuracy, and also as a backup orbit determination system for large satellites.