Sensitivity of the Gravity Model and Orbital Frame for On-board Real-Time Orbit Determination: Operational Results of GPS-12 GPS Receiver

Eunhyouek Kim,Seungyeop Han,Amer Mohammad Al Sayegh

doi:10.3390/rs11131542

Eunhyouek Kim, Seungyeop Han + Show 1 more

Open Access

https://doi.org/10.3390/rs11131542

Copy DOI

Journal: Remote Sensing	Publication Date: Jun 28, 2019
Citations: 1	License type: CC BY 4.0

Affiliation: Mohammed Bin Rashid School of Government

Abstract

This paper describes the sensitivity of both the orbital frame domain selection and the gravity model on the performance of on-board real-time orbit determination. Practical error sources, which affect the navigation solution of spaceborne global positioning system (GPS) receivers, are analyzed first. Then, a reasonable orbital frame (radial, in-track, cross-track (RIC)) is proposed to clearly represent the characteristics of the error in order to improve the performance of the orbit determination (OD) logic. In addition, the sensitivity of the gravity model affecting the orbit determination logic is analyzed by comparison with the precise orbit ephemeris (POE) of the Challenging Minisatellite Payload (CHAMP) satellite, and it is confirmed that the Gravity Recovery And Climate Experiment (GRACE) Gravity Model 03 (GGM03) outperforms the Earth Gravity Model 1996 (EGM96). The effects of both proposed orbit frames and the gravity model on the orbit determination logic are verified using a GPS simulator and observation data from the CHAMP satellite. Moreover, the practical performance of on-board real-time orbit determination logic is verified by updating the software of the spaceborne GPS receiver, GPS-12, on DubaiSat-2 operating at low Earth orbit (LEO). The results show that the position accuracy of on-board real-time orbit determination logic in GPS-12 is improved by 59%, from 12.6 m (1 σ) to 5.1 m (1 σ), after applying the proposed methods. The velocity accuracy is also improved by 57%, from 13.7 mm/s (1 σ) to 5.9 mm/s (1 σ).

Highlights

Today, satellites depend entirely on global positioning system (GPS) receivers to acquire the current time and to synchronize each subsystem
The navigation solution generated by the standard positioning service (SPS) logic of the GPS receiver operating at low Earth orbit (LEO) is degraded by ephemeris message error, signal noise, ionospheric time delay, and so on
After applying the high precision orbit propagator (HPOP) on the on-board real-time orbit determination logic of GPS-12, the accuracy of the navigation solution improved by about 50%, from about 26 m (1 σ) to about 13 m (1 σ) [12]

Summary

Introduction

Satellites depend entirely on GPS receivers to acquire the current time and to synchronize each subsystem. After applying the HPOP on the on-board real-time orbit determination logic of GPS-12, the accuracy of the navigation solution improved by about 50%, from about 26 m (1 σ) to about 13 m (1 σ) [12]. If the orbit determination logic is designed on the orbital frame, which has a position vector like the RIC frame, the covariance of the measurement noise can be designed more precisely, and it will improve the performance of the navigation solutions. To confirm its effectiveness in reducing the ionospheric time delay, the accuracy of the orbit determination logic was analyzed on the RIC frame using the reference orbit from the GPS simulator. The sensitivity of the gravity model is analyzed according to EGM96 and GGM03

Test Configuration for Efficacy Verification

Test Configuration for Effic8a0cy Verification

60 J2 Kozai

Findings

In-orbit Performance of On-board Real-time Orbit Determination Logic