GEO Broadcast Ephemeris Parameter Fitting Compatible with GPS LNAV User Algorithm

Jaeuk Park, Changdon Kee, and Juhyun Maeng

Abstract: Due to its low eccentric and inclination angle, geostationary orbit (GEO) suffer from the singularity in orbital elements. During the fitting process for broadcast ephemeris parameter in navigation message, this singularity can make performance objective illconditioned thereby resulting in degradation of fit accuracy of ephemeris. There have been two major solutions known for this singularity: one is rotation of the reference plane defining inclination angle and the other is to adoption of new broadcast ephemeris parameters. Unfortunately, either way required change of broadcast ephemeris user algorithm so that a distinct user algorithm just for GEO navigation satellites was needed. In order to resolve GEO singularity without change of user algorithm, in this study, we analyzed a target fitting algorithm which applies inverse mapping from 5 nonsingular elements to original ephemeris parameters. Those nonsingular elements were utilized to resolve singularity during fitting process, and they were mapped inversely to original GPS legacy navigation message (GPS LNAV) broadcast ephemeris parameters after convergence so that user can utilize the fitting result by the GPS LNAV user algorithm, which is most commonly used in navigation satellite system. To assess the performance of the target fitting algorithm, we performed fitting experiments with 24-hour simulated navigation satellites in GEO. Fitted broadcast ephemeris parameters of the target algorithm were relatively stable compared to the results of the fitting algorithm without the resolution of GEO singularity. Furthermore, we found that the target fitting algorithm can provide 1 cm and 0.1 mm/s level of fit accuracy for satellite position and velocity without the change of user algorithm, which were similar to that of the existing BeiDou GEO fitting algorithm with change of user algorithm.
Published in: Proceedings of the ION 2024 Pacific PNT Meeting
April 15 - 18, 2024
Hilton Waikiki Beach
Honolulu, Hawaii
Pages: 228 - 237
Cite this article: Park, Jaeuk, Kee, Changdon, Maeng, Juhyun, "GEO Broadcast Ephemeris Parameter Fitting Compatible with GPS LNAV User Algorithm," Proceedings of the ION 2024 Pacific PNT Meeting, Honolulu, Hawaii, April 2024, pp. 228-237.
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