Satellite Ephemeris Approximation Methods to Support Lunar Positioning, Navigation, and Timing Services

Marta Cortinovis, Keidai Iiyama, Grace Gao

Peer Reviewed

Abstract: Plans to establish a satellite network around the Moon to support communication, position, navigation, and timing services are rapidly evolving. Satellites that are part of this system broadcast their ephemeris as finite parameters to lunar users for user state estimation. We investigate lunar satellite ephemeris parameterization to identify the optimal parameterization to broadcast to a lunar user. The proposed framework directly approximates the lunar satellite position and velocity in the inertial frame, along with approximating conversion parameters necessary for representation in the lunar fixed frame. The framework leverages signal-in-space-error requirements as constraints in the approximation process to guide the search for the best parameterization. We evaluate the performance of our proposed framework for satellites in a Low Lunar Orbit and an Elliptical Lunar Frozen Orbit. The performance of different methods is assessed based on the precision of the ephemeris prediction, approximation interval, and message size. We showcase the ability of the developed framework to approximate satellite ephemeris for both orbits to the desired precision by adjusting the approximation period and the number of broadcasted parameters. Particularly, we demonstrate that model formulations with a standard polynomial basis and a Chebyshev polynomial basis produce feasible solutions for ephemeris approximation at varying epochs in orbits, abiding by stringent signal-in-space-error requirements.
Published in: Proceedings of the 36th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2023)
September 11 - 15, 2023
Hyatt Regency Denver
Denver, Colorado
Pages: 3647 - 3663
Cite this article: Cortinovis, Marta, Iiyama, Keidai, Gao, Grace, "Satellite Ephemeris Approximation Methods to Support Lunar Positioning, Navigation, and Timing Services," Proceedings of the 36th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2023), Denver, Colorado, September 2023, pp. 3647-3663. https://doi.org/10.33012/2023.19282
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