Filter Smoothing for Spacecraft Navigation

Cole A. Sherling, Will Driessen, Heying Zhang, Michael R. Walker II, and John A. Christian

Abstract:	Accurate state estimation for spacecraft navigation is dependent upon receiving reliable measurements from various onboard sensors. However, state estimation accuracy may be impaired when measurements are unavailable due to communication loss, signal interference, hardware failure, or other undesirable conditions. Filter smoothing can enhance state estimation in periods of travel where measurement dropouts occur by utilizing existing estimates from a navigation filter and measurements from after the dropout. This study evaluates the performance of the Fraser-Potter smoother for satellite navigation in lunar orbit, with measurements available only in regions with direct line of sight to lunar surface beacons. Additionally, this work identifies the filter convergence ratio as a metric to predict the performance of the Fraser-Potter smoother in real-time applications.
Published in:	Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025) September 8 - 12, 2025 Hilton Baltimore Inner Harbor Baltimore, Maryland
Pages:	823 - 833
Cite this article:	Sherling, Cole A., Driessen, Will, Zhang, Heying, Walker, Michael R., II, Christian, John A., "Filter Smoothing for Spacecraft Navigation," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 823-833. https://doi.org/10.33012/2025.20372
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