Opportunistic LEO PNT via Ground Segment Ephemeris Product Provision

Samer Hayek, Joe Saroufim, and Zaher M. Kassas

Peer Reviewed

Abstract:	This paper formulates the design of a ground segment enabling accurate opportunistic low Earth orbit (LEO) positioning, navigation, and timing (PNT) with non-cooperative satellites. A reference receiver with known position estimates a noncooperative LEO satellite’s dynamic states, namely its position and velocity, via navigation observables derived from the satellite’s transmitted downlink signals. The reference receiver communicates an ephemeris message with navigating users, significantly improving their opportunistic LEO PNT accuracy. Experimental results are presented, demonstrating the efficacy of the proposed approach with Doppler measurements from 48 Starlink LEO satellites, where the ephemeris message was communicated from the reference receiver to a stationary user, both located in Columbus, Ohio, USA, over a 6.92 km baseline. Via Monte Carlo analysis with an average two-dimensional initial position error of 11.66 km, it is shown that if the user utilized publicly available ephemerides data, namely (i) general perturbations elements and (ii) supplemental GP elements, the achieved horizontal and vertical positioning errors were (i) 2,962 m and 554 m and (ii) 781 m and 151 m, respectively. In contrast, utilizing the proposed ground segment, the horizontal and vertical positioning errors reduce to 4.97 m and 25.36 m, respectively.
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:	2074 - 2084
Cite this article:	Hayek, Samer, Saroufim, Joe, Kassas, Zaher M., "Opportunistic LEO PNT via Ground Segment Ephemeris Product Provision," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 2074-2084. https://doi.org/10.33012/2025.20472
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