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Yang Y.,Northwestern Polytechnical University | Yang Y.,National Key Laboratory of Aerospace Flight Dynamics AFDL | Yue X.,Northwestern Polytechnical University | Yue X.,National Key Laboratory of Aerospace Flight Dynamics AFDL | And 3 more authors.
Lecture Notes in Electrical Engineering | Year: 2015

Nowadays, satellites in low earth orbit (LEO) can benefit from Global Navigation Satellite System (GNSS), such as Global Positioning System (GPS) of United States, to estimate positions and velocities. As China’s BeiDou Navigation Satellite System (BDS) has been formally operational since the end of 2012, standalone Beidou and combined GPS + Beidou positioning techniques tend to be applied in the future space missions. However, no LEO satellites have been operated with Beidou receivers at present. Hence Beidou-based precise orbit determination (POD) technique is required to be tested and verified on ground at first stage. This study is to test the GPS + Beidou orbit determination software in ground testbed. GNSS data collected from iGMAS (International GNSS Monitoring and Assessment Service) and MGEX (Multi-GNSS Experiment) stations are processed in both static and kinematic PPP (Precise Point Positioning) modes. Decimetre level of positioning accuracy is achieved. The inter-system biases between GPS and Beidou are estimated and analysed. Results indicate that GPS + Beidou solutions are more precise than the standalone GPS solutions. © Springer-Verlag Berlin Heidelberg 2015. Source


Yang Y.,Northwestern Polytechnical University | Yang Y.,National Key Laboratory of Aerospace Flight Dynamics AFDL | Yue X.,Northwestern Polytechnical University | Yue X.,National Key Laboratory of Aerospace Flight Dynamics AFDL | And 3 more authors.
Advances in Space Research | Year: 2014

Clock error estimation has been the focus of a great deal of research because of the extensive usage of clocks in GPS positioning applications. The receiver clock error in the spacecraft orbit determination is commonly estimated on an epoch-by-epoch basis, along with the spacecraft's position. However, due to the high correlation between the spacecraft orbit altitude and the receiver clock parameters, estimates of the radial component are degraded in the kinematic approach. Using clocks with high stability, the predictable behaviour of the receiver oscillator can be exploited to improve the positioning accuracy, especially for the radial component. This paper introduces two GPS receiver clock models to describe the deterministic and stochastic property of the receiver clock, both of which can improve the accuracy of kinematic orbit determination for spacecraft in low earth orbit. In particular, the clock parameters are estimated as time offset and frequency offset in the two-state model. The frequency drift is also estimated as an unknown parameter in the three-state model. Additionally, residual non-deterministic random errors such as frequency white noise, frequency random walk noise and frequency random run noise are modelled. Test results indicate that the positioning accuracy could be improved significantly using one day of GRACE flight data. In particular, the error of the radial component was reduced by over 40.0% in the real-time scenario. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved. Source


Yang Y.,Northwestern Polytechnical University | Yang Y.,National Key Laboratory of Aerospace Flight Dynamics AFDL | Yue X.,Northwestern Polytechnical University | Yue X.,National Key Laboratory of Aerospace Flight Dynamics AFDL | And 2 more authors.
International Journal of Aerospace Engineering | Year: 2015

With the ever-increasing number of satellites in Low Earth Orbit (LEO) for scientific missions, the precise determination of the position and velocity of the satellite is a necessity. GPS (Global Positioning System) based reduced-dynamic orbit determination (RPOD) method is commonly used in the post processing with high precision. This paper presents a sequential RPOD strategy for LEO satellite in the framework of Extended Kalman Filter (EKF). Precise Point Positioning (PPP) technique is used to process the GPS observations, with carrier phase ambiguity resolution using Integer Phase Clocks (IPCs) products. A set of GRACE (Gravity Recovery And Climate Experiment) mission data is used to test and validate the RPOD performance. Results indicate that orbit determination accuracy could be improved by 15% in terms of 3D RMS error in comparison with traditional RPOD method with float ambiguity solutions. © 2015 Yang Yang et al. Source

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