Abstract

Traditional precise orbit determination (POD) for low Earth orbit (LEO) satellites relies on observations from ground stations and onboard receivers. Although the accuracy can reach centimeter level, there are still problems such as insufficient autonomous operation capability. The inter-satellite link (ISL) is a link used for communication between satellites and has a function of dual-way ranging. Numerous studies have shown that observational data using ISLs can be adopted for POD of navigation satellites. In this contribution, we mainly focus on LEO satellites POD with ISLs. First, we design LEO constellations with different numbers of satellites and ISL measurements, based on which the constellations are simulated. Then rough tests of POD using different link topologies are carried out. The results show that in the 60-LEO constellation the average 3-dimensional (3D) orbital errors are 0.112 m using “4-connected” link topology with constant 4 links per satellite and 0.069 m using “all-connected” link topology with theoretically maximum numbers of links. After that, we carry out refined POD experiments with several sets of satellite numbers and different observation accuracy. The results show the higher link ranging accuracy and the more numbers of links bring higher POD precision. POD with ISLs gets bad performance in the case of center of gravity reference when link ranging accuracy is poor and numbers of links are small. When the link accuracy is 40 cm, average 3D orbital errors of 60-LEO constellation are 0.358 m, which can only meet the demand of autonomous navigation. With the constraint of the right ascension of the ascending node (RAAN), POD using ISLs reaches an extremely high precision when adopting a spatial reference provided by navigation satellites. For 120-LEO constellation, the average 3D orbital errors are 0.010 m; for 192-LEO constellation, the errors are 0.006 m.

Highlights

  • The precise orbit determination (POD) of satellite refers to the process of obtaining the accurate state vectors of satellites in a certain epoch by handling satellite orbital measurements with the estimation strategies like least squares or Kalman filtering [1,2]

  • Our study mainly focuses on preliminary evaluation of the performance of low Earth orbit (LEO) satellite POD with inter-satellite link (ISL) measurements

  • POD results with center of gravity reference are shown and we concentrate on analyzing the impact of link ranging accuracy and the numbers of links on the performance of POD

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Summary

Introduction

The precise orbit determination (POD) of satellite refers to the process of obtaining the accurate state vectors of satellites in a certain epoch by handling satellite orbital measurements with the estimation strategies like least squares or Kalman filtering [1,2]. The measurement technique exploits a decisive role in the accuracy of the POD process, and the selection of the POD method should be adapted to the orbit measuring technology, combined with the actual situation of the satellites and the users’ needs [3]. With the refinement of force model as well as the improvement of data processing strategy, POD for GNSS satellites can reach an accuracy of centimeter level [4,5]. Once ground receivers lose communication with the satellites because of crisis situation like equipment downtime, orbit determination becomes a problem

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