Earth Rotation Parameters Estimation Using GPS and SLR Measurements to Multiple LEO Satellites

Xingxing Li,Keke Zhang,Yongqiang Yuan,Hongmin Zhang,Yujie Qin,Wei Zhang

doi:10.3390/rs13153046

Abstract

Earth rotation parameters (ERP) are one of the key parameters in realization of the International Terrestrial Reference Frames (ITRF). At present, the International Laser Ranging Service (ILRS) generates the satellite laser ranging (SLR)-based ERP products only using SLR observations to Laser Geodynamics Satellite (LAGEOS) and Etalon satellites. Apart from these geodetic satellites, many low Earth orbit (LEO) satellites of Earth observation missions are also equipped with laser retroreflector arrays, and produce a large number of SLR observations, which are only used for orbit validation. In this study, we focus on the contribution of multiple LEO satellites to ERP estimation. The SLR and Global Positioning System (GPS) observations of the current seven LEO satellites (Swarm-A/B/C, Gravity Recovery and Climate Experiment (GRACE)-C/D, and Sentinel-3A/B) are used. Several schemes are designed to investigate the impact of LEO orbit improvement, the ERP quality of the single-LEO solutions, and the contribution of multiple LEO combinations. We find that ERP estimation using an ambiguity-fixed orbit can attain a better result than that using ambiguity-float orbit. The introduction of an ambiguity-fixed orbit contributes to an accuracy improvement of 0.5%, 1.1% and 15% for X pole, Y pole and station coordinates, respectively. In the multiple LEO satellite solutions, the quality of ERP and station coordinates can be improved gradually with the increase in the involved LEO satellites. The accuracy of X pole, Y pole and length-of-day (LOD) is improved by 57.5%, 57.6% and 43.8%, respectively, when the LEO number increases from three to seven. Moreover, the combination of multiple LEO satellites is able to weaken the orbit-related signal existing in the single-LEO solution. We also investigate the combination of LEO satellites and LAGEOS satellites in the ERP estimation. Compared to the LAGEOS solution, the combination leads to an accuracy improvement of 0.6445 ms, 0.6288 ms and 0.0276 ms for X pole, Y pole and LOD, respectively. In addition, we explore the feasibility of a one-step method, in which ERP and the orbit parameters are jointly determined, based on SLR and GPS observations, and present a detailed comparison between the one-step solution and two-step solution.

Highlights

Changing of global ice, ocean and atmosphere, the core–mantle interaction torques, and the gravitational attraction of the sun, moon, and planets [1,2] give rise to the variations of earth rotation
The goal of this study is to investigate the contribution of multiple low Earth orbit (LEO) satellites to the Earth rotation parameters (ERP) estimation with seven LEO satellites flying at different orbits
A large amount of satellite laser ranging (SLR) observations to LEO satellites offer an opportunity for investigating the potential of LEO satellites in ERP estimation

Summary

Introduction

Changing of global ice, ocean and atmosphere, the core–mantle interaction torques, and the gravitational attraction of the sun, moon, and planets [1,2] give rise to the variations of earth rotation. These effects can be comprehensively described by defining a set of parameters, namely, Earth rotation parameters (ERP), which consist of pole coordinates and universal time 1—universal time coordinated (UT1-UTC) or its first derivative in time, denoted as length-of-day (LOD). International Earth Rotation and Reference Systems Service (IERS), based on different space geodetic techniques. A number of low Earth orbit (LEO) satellites carry retroreflectors for tracking and navigation purposes, Laser Geodynamics Satellites (LAGEOS) and Etalons are the satellites that are most commonly used to determine the

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