Abstract
An algorithm for real-time and onboard orbit determination applying the Extended Kalman Filter (EKF) method is developed. Aiming at a very simple and still fairly accurate orbit determination, an analysis is performed to ascertain an adequacy of modeling complexity versus accuracy. The minimum set of to-be-estimated states to reach the level of accuracy of tens of meters is found to have at least the position, velocity, and user clock offset components. The dynamical model is assessed through several tests, covering force model, numerical integration scheme and step size, and simplified variational equations. The measurement model includes only relevant effects to the order of meters. The EKF method is chosen to be the simplest real-time estimation algorithm with adequate tuning of its parameters. In the developed procedure, the obtained position and velocity errors along a day vary from 15 to 20 m and from 0.014 to 0.018 m/s, respectively, with standard deviation from 6 to 10 m and from 0.006 to 0.008 m/s, respectively, with the SA either on or off. The results, as well as analysis of the final adopted models used, are presented in this work.
Highlights
The Global Positioning System (GPS) is a satellite navigation system that has been used to determine the position, velocity, and time with high accuracy of an artificial satellite, such as TOPEX/POSEIDON (T/P) [1], Jason-1, Jason-2, CHAllenging Minisatellite Payload (CHAMP), and GRACE satellites
The TOPEX/POSEIDON (T/P) mission is jointly conducted by the United States National Aeronautics and Space Administration (NASA) and the French Space Agency, Centre National d’Etudes Spatiales (CNES)
Pardal et al [15] determined the orbit of an artificial satellite and analyzed its implications, using least squares algorithms through sequential given rotations as the method of estimation, and data of the GPS receivers
Summary
The Global Positioning System (GPS) is a satellite navigation system that has been used to determine the position, velocity, and time with high accuracy of an artificial satellite, such as TOPEX/POSEIDON (T/P) [1], Jason-1, Jason-2, CHAMP, and GRACE satellites. Pardal et al [15] determined the orbit of an artificial satellite and analyzed its implications, using least squares algorithms through sequential given rotations as the method of estimation, and data of the GPS receivers This approach has the goal of improving the performance of the orbit estimation process and, at the same time, of minimizing the computational procedure cost. An algorithm to determine onboard the satellite orbit in real-time using the GPS system and Kalman filtering is developed It used a simplified and compact model with low computational cost. The raw single frequency pseudorange GPS measurements are used as observations by the Kalman filter They are modeled taking into account most of the GPS satellite and receiver clock offsets. The target is orbit accuracy in the order of tens of meters with simple modeling of the dynamics or measurement systems, and still keeping low requirements of speed and computational burden
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