Demonstration of Adaptive Extended Kalman Filter for Low Earth Orbit Formation Estimation Using CDGPS

Franz D. Busse, Jonathan P. How and James Simpson

Abstract:	Carrier-phase Differential GPS is an ideal sensor for formation flying missions in low Earth orbit since it provides a direct measure of the relative positions and velocities of the vehicles in the fleet. This paper presents results for a relative navigation filter that achieves centimeter-level precision using measurements from a customized GPS receiver. This work uses a precise, robust extended Kalman filter that is based on relatively simple measurement models and a linear Keplerian propagation model. To increase the robustness of the filter in the face of environment uncertainty, the filter is adapted using MMLE algorithms. The adaptive filter is used to accurately identify the process noise and sensor noise covariance for the system. Despite the simplicity of the filter, hardware-in-the-loop simulations performed on the Formation Flying Testbed at the Goddard Space Flight Center demonstrate that this filter can achieve ~=2 cm relative position accuracy and <0.5 mm/s relative velocity accuracy for a range of Low Earth Orbit formations.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	2047 - 2058
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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