An ephemeris error correction scheme enabling accurate positioning, navigation, and timing (PNT) with low Earth orbit (LEO) satellites whose ephemerides are poorly known is developed. A reference receiver with known position estimates two parameters: three-dimensional (3-D) ephemeris error magnitude and its direction angle from the in-track axis, which are shown to be sufficient to parameterize a significant amount of a LEO space vehicle’s (SV’s) ephemeris error. The parameters are communicated to an unknown receiver listening to the same LEO SVs to correct its extracted LEO ranging measurements leading to significantly improve its PNT accuracy. Simulation results are presented of an aerial vehicle navigating over Salt Lake City, Utah, USA, with pseudorange observables from overhead Starlink, Orbcomm, Iridium, and Globalstar LEO SVs, fused in a tightly-coupled LEO-aided inertial measurement unit (IMU) fashion. The vehicle employed LEO ephemeris corrections communicated by two reference stations located in Arizona and Nevada, USA, over baseline distances of 633 km and 511 km, respectively, enabling the vehicle to achieve a three-dimensional (3-D) position root-mean square error (RMSE) of 10.9 m over a trajectory of 48.14 km without global navigation satellite system (GNSS) signals. Experimental results are presented in which the ephemeris corrections of 7 Starlink, 2 Orbcomm, 1 OneWeb, and 1 Iridium SVs were computed on a ground vehicle during a GNSS availability period of 8 s, after which GNSS signals were cut off and the vehicle navigated for 1.36 km with LEO carrier phase measurements, achieving a 3-D RMSE of 7.83 m.
LEO Ephemeris Error Modeling Enabling Long Baseline Correction for Improved PNT
2025-04-28
4254408 byte
Conference paper
Electronic Resource
English
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