Effect of Higher-Order Ionospheric Delay on Precise Orbit Determination of GRACE-FO Based on Satellite-Borne GPS Technique

Linhu Qi,Zhouming Yang,Jinyun Guo,Yaowei Xia

doi:10.1109/access.2021.3059296

Abstract

Ionospheric delay is one of the main errors in precise orbit determination (POD) of Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) with satellite-borne GPS technique. Effective elimination or reduction of ionospheric delay can improve POD precision. For satellite-borne GPS dual-frequency data, the ionospheric-free linear combination is generally used to eliminate the first-order term, while igoring the influence of higher-order terms. To improve the POD precision of GRACE-FO, this paper presents an effective method to calculate higher-order ionospheric delay of GRACE-FO observation. Dual-frequency GPS receiver observation is used to calculate the total electron content on the signal propagation path. The magnetic field strength is calculated according to international geomagnetic reference field model, and the angle between the GPS signal propagation path and the geomagnetic field is calculated. Finally, the delays of second-order and third-order terms are calculated and introduced into GRACE-FO reduced-dynamic POD. The effect of higher-order ionospheric delay on POD of GRACE-FO is analyzed in detail. The results show that the influence of ionospheric higher-order term on satellite-borne GPS observation is in centimeter level. The orbit precision of GRACE-FO can be improved by adding higher-order ionospheric delay, with improvement order of sub-millimeter level.

Highlights

Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) is a joint mission launched by National Aeronautics and Space Administration (NASA) and German Research Centre for Geosciences (GFZ) on May 22, 2018
OF precise orbit determination (POD) In order to study the influence of high-order ionospheric delay on POD precision of GRACE-FO, the method of simplified dynamics is used for POD
The precise orbit of GRACE-FO without high-order ionospheric delay correction is obtained by using the 15-day unprocessed observations of DOY 71-85 in 2019

Summary

Introduction

Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) is a joint mission launched by National Aeronautics and Space Administration (NASA) and German Research Centre for Geosciences (GFZ) on May 22, 2018. Its purpose is to replace the Gravity Recovery and Climate Experiment (GRACE) that was decommissioned in June 2017 after performed in orbit for 15 years, and to use twin satellites to accurately map the earth’s gravity field [1], [2]. Like GRACE satellites, GRACE-FO satellites are equipped with GPS receivers, K-Band Ranging System (KBR), laser retroreflectors and other scientific instruments [3]. Precise satellite orbits can ensure precise processing of gravity data, which is helpful for the estimation of gravity models and the acquisition of global gravity field products.

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Results

Conclusion