Assessing antenna field of view and receiver clocks of COSMIC and GRACE satellites: lessons for COSMIC-2
- 706 Downloads
We provide suggestions for the approved COSMIC-2 satellite mission regarding the field of view (FOV) and the clock stability of its future GNSS receiver based on numerical analyses using COSMIC GPS data. While the GRACE GPS receiver is mounted on the zenith direction, the precise orbit determination (POD) antennas of COSMIC are not. The COSMIC antenna design results in a narrow FOV and a reduction in the number of GPS observations. To strengthen the GPS geometry, GPS data from two POD antennas of COSMIC are used to estimate its orbits. The phase residuals of COSMIC are at the centimeter level, compared to the millimeter level of GRACE. The receiver clock corrections of COSMIC and GRACE are at the microsecond and nanosecond levels, respectively. The clock spectra of COSMIC at the frequencies of 0–0.005 Hz contain significant powers, indicating potential systematic errors in its clock corrections. The clock stability, expressed by the Allan deviation, of COSMIC ranges from 10−9 to 10−11 over 1 to 104 s, compared to 10−12 to 10−14 for GRACE. Compared to USO-based clock of GRACE, the clock of COSMIC is degraded in its stability and is linked to the reduction of GPS data quality. Lessons for improvement of COSMIC-2 over COSMIC in FOV and receiver clock stability are given.
KeywordsClock stability COSMIC Field of view GPS Precise orbit determination
This research is supported by National Space Organization, Taiwan (contract no. NSPO-S-100011), Australia Space Research Program (ASRP) (Grant No. ASRP2, RMIT), and National Science Council (contract no. 100-2221-E-009-132-MY3). We thank CODE for providing the precise GPS orbit, clock, and earth rotation parameters and are grateful to the comments of reviewers to enhance the quality of the paper.
- Allan DW (1987) Time and frequency (time-domain) characterization, estimation, and prediction of precision clock and oscillators. IEEE Trans Ultrason Ferroelect Freq Contr, vol.uffc-34(6)Google Scholar
- Bettadpur S (2012) GRACE Product Specification Document, Rev. 4.6. Technical Report GRACE 327-720 (CSR-GR-03-02), Center for Space Research, The University of Texas at AustinGoogle Scholar
- Dach R, Hugentobler U, Fridez P, Meindl M (2007) Bernese GPS Software—Version 5.0, Astronomical Institute. University of Bern, SwitzerlandGoogle Scholar
- Esterhuizen S, Franklin G, Hurst K, Mannucci A, Meehan T, Webb F, Young L (2009) TriG—A GNSS precise orbit and radio occultation space receiver. 22nd International meeting of the satellite division of the institute of navigation, Savannah, GA, September 22-25, page(s):1442–1446Google Scholar
- Hofmann-Wellenhof B, Lichtenegger H, Collins J (2001) Global positioning system: theory and practice. Springer Wien New York, ISBN 3-211-83472-9Google Scholar
- Kuang D, Bertiger W, Desai S, Haines B, Iijima B, Meehan T (2008) Precise orbit determination for COSMIC Satellites using GPS data from two on-board Antennas. Proceedings of the IEEE/ION PLANS, pp 720–730, May 6–8, Monterey, CaliforniaGoogle Scholar
- Riley WJ (2003) Techniques for frequency stability analysis. IEEE International Frequency Control Symposium, Tampa, FL, May 4Google Scholar