1. Key Laboratory of Geospace Environment and Geodesy, School of Geodesy and Geomatics; Wuhan University; Wuhan China
2. State Key Laboratory of Geodesy and Earth's Dynamics; Institute of Geodesy and Geophysics, Chinese Academy of Science; Wuhan China
3. National Oceanic and Atmospheric Administration; Silver Spring Maryland USA
4. Shanghai Astronomical Observatory, Chinese Academy of Science; Shanghai China