LEO Satellite Clock Modeling and Its Benefits for LEO Kinematic POD
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Published:2023-06-16
Issue:12
Volume:15
Page:3149
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ISSN:2072-4292
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Container-title:Remote Sensing
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language:en
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Short-container-title:Remote Sensing
Author:
Wang Kan12ORCID, El-Mowafy Ahmed3ORCID, Yang Xuhai12
Affiliation:
1. National Time Service Center, Chinese Academy of Sciences, Xi’an 710600, China 2. University of Chinese Academy of Sciences, Beijing 100049, China 3. School of Earth and Planetary Sciences, Curtin University, Perth, WA 6845, Australia
Abstract
High-accuracy Low Earth Orbit (LEO) satellite clock and orbital products are preconditions to realize LEO augmentation for high-accuracy GNSS-based positioning on the ground. There is a high correlation between the orbit and clock parameters in the kinematic Precise Orbit Determination (POD) process. While future LEO satellites are planned to be equipped with better clocks, the benefits of modeling high-stability LEO satellite clocks are not yet thoroughly investigated, particularly when mid- to long-term systematic effects induced by the complex LEO relativistic effects and the external environment remain in the clocks. Through clock modeling, this study attempts to reduce not only the short-term noise of radial kinematic orbits, but also mis-modeled effects caused by, e.g., real-time GNSS orbital and clock errors. To explore the benefits of clock modeling, the clocks need to be first detrended by the mid- to long-term systematic effects. While over-detrending limits the orbital improvements, weak detrending would also hamper strong clock modeling and easily lead to performance degradations. A balance between the strengths of the detrending and the model thus needs to be investigated for different clock types. In this study, the Piece-Wise Linear (PWL) model of different time lengths and a 2.5-state filter with different strengths (h values) are tested using real data from GRACE FO-1 with an Ultra-Stable Oscillator (USO) on board. Using the CNES real-time GPS products, it was found that when detrending the clocks with a smoothing window of 300 to 500 s, one could generally expect an improvement larger than 10% in the estimation of radial orbits when applying a PWL model with a length from 300 to 1200 s. Improvements of this size can also be expected when using the 2.5-state model with h−1 (for Flicker Frequency Noise) from 10−28 to 10−30.
Funder
National Natural Science Foundation of China CAS “Light of West China” Program National Time Service Center, Chinese Academy of Sciences Shaanxi Province Key R&D Program Project Australian Research Council
Subject
General Earth and Planetary Sciences
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