Study on Optimal Broadcast Ephemeris Parameters for GEO/IGSO Navigation Satellites.

Chandeok Park,Gimin Kim,Jin Haeng Choi,Deok Won Lim

doi:10.3390/s20226544

Chandeok Park, Gimin Kim + Show 2 more

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https://doi.org/10.3390/s20226544

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Abstract

This paper proposes new sets of suitable broadcast ephemeris parameters for geosynchronous (GEO) and inclined geosynchronous (IGSO) navigation satellites (NSs). Despite the increasing number of GEO and IGSO NSs, global positioning system (GPS)-type ephemeris parameters are still widely used for them. In an effort to provide higher fit accuracy, we analyze a variety of broadcast ephemeris parameters for GEO and IGSO satellites along with their orbital characteristics and propose optimal sets of parameters. Nonsingular elements and orbital plane rotation are adopted for alleviating/avoiding the singularity issues of GEO satellites. On the basis of 16 parameters of GPS LNAV, we add one to four parameters out of 28 correction ones to determine optimal sets of ephemeris parameters providing higher accuracy. All possible parameter sets are tested with the least-square curve fit for four BeiDou GEOs and six BeiDou IGSOs. Their fit accuracies are compared to determine the optimal broadcast ephemeris parameters that provide minimum fit errors. The set of optimal ephemeris parameters depends on the type of orbit. User range error (URE) accuracies of the proposed optimal ephemeris parameters ensure results within 2.4 cm for IGSO and 3.8 cm for GEO NSs. Moreover, the experimental results present common parameter sets for both IGSO and GEO for compatibility and uniformity. Compared with four conventional/well-known sets of ephemeris parameters for BeiDou, our proposed parameters can enhance accuracies of up to 34.5% in terms of URE. We also apply the proposed optimal parameter sets to one GEO and three IGSO satellites of QZSS. The effects of fitting intervals, number of parameters, total bits, and orbit types on the fit accuracy are addressed in detail.

Highlights

The navigation message, which is the final form of navigation data received by users, provides the location of navigation satellites (NSs)
Referring to Montenbruck et al [27], which addressed the proper values of weighted factors for inclined geosynchronous (IGSO)/GEO satellites of BeiDou, we set = (0.99, 1/126)
For IGSO satellites, our parameter sets 1–4 ensured that root mean square (RMS) errors of R/T/N components were less than 8.9/10.1/1.72 cm for J01, 3.0/5.9/5.3 cm for J02, and 3.0/7.0/4.3 cm for J03

Summary

Introduction

The navigation message, which is the final form of navigation data received by users, provides the location of navigation satellites (NSs). Users conduct navigation and positioning on the basis of the satellite location obtained from this message. As satellite locations are given in the form of ephemerides parameters for fitting, their fit performance directly influences navigation and positioning accuracy [1,2,3]. It is significantly important to design a set of appropriate/optimal broadcast ephemeris parameters in the navigation satellite system. There exist two types of broadcast ephemeris parameters in general: Cartesian-based and Keplerian-based models. The Cartesian-based model describes the perturbed satellite orbit with instantaneous satellite position/velocity and lunisolar acceleration in the Earth-centered Earth-fixed (ECEF) coordinate system. It effectively estimates the position and velocity of satellites without singularity. The Keplerian-based model, on the other hand, describes the perturbed satellite orbit with

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