Abstract
Low Earth Orbit (LEO) satellites can be used for remote sensing and gravity field recovery, while precise orbit determination (POD) is vital for LEO satellite applications. However, there are some systematic errors when using the LEO satellite orbits released by different agencies in multi-satellite-based applications, e.g., Swarm and Gravity Recovery and Climate Experiment-Follow-On (GRACE-FO), as different GNSS precise orbit and clock products are used as well as processing strategies and software. In this paper, we performed undifferenced kinematic PODs for Swarm and GRACE-FO satellites simultaneously over a total of 14 days by using consistent International Global Navigation Satellite System (GNSS) Service (IGS) precise orbit and clock products. The processing strategy based on an undifferenced ionosphere-free combination and a least squares method was applied for Swarm and GRACE-FO satellites. Furthermore, the quality control for the kinematic orbits was adopted to mitigate abrupt position offsets. Moreover, the accuracy of the kinematic orbits solution was evaluated by carrier phase residual analysis and Satellite Laser Ranging (SLR) observations, as well as comparison with official orbits. The results show that the kinematic orbits solution is better than 4 cm, according to the SLR validation. With quality control, the accuracy of the kinematic orbit solution is improved by 2.49 % for the Swarm-C satellite and 6.98 % for the GRACE-D satellite when compared with their precise orbits. By analyzing the accuracy of the undifferenced kinematic orbit solution, the reliability of the LEO orbit determination is presented in terms of processing strategies and quality control procedures.
Highlights
Low Earth Orbit (LEO) satellite is a valuable platform for Earth observation due to the low altitude, short period, and rapid connection with the ground [1]
Results and Analysis the In satellite orbiting results. They were close to the observation noise level when the this paper, the performance of kinematic orbits and reduced dynamic orbits soluquality of the observations and the preprocessing results were satisfactory [33]
Analyzing the number of tracked GPS satellites after data preprocessing and the RTN accelerations estimated by Reduced Dynamic POD (RDPOD) for Swarm-C on day of year (DOY) 162, we found that lots of observa7 of 18 tions between 14:00 and 16:00 were deleted during data preprocessing, resulting in a fewer number of observations than six in many epochs
Summary
Low Earth Orbit (LEO) satellite is a valuable platform for Earth observation due to the low altitude, short period, and rapid connection with the ground [1]. To ensure successful scientific applications undertaken by the LEO satellite, the precise orbit determination (POD) for the LEO satellite is essential. National d’Etudes Spatiales (CNES) in 1992, satellite-borne GPS technology has been utilized to obtain a high-accuracy centimeter-level orbit. The on-board GNSS receivers have been applied to achieve high-accuracy orbital information in the subsequent LEO satellite missions. Kinematic POD (KPOD) of LEO satellites does not rely on any orbital dynamics model and can achieve high-precision results.
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