Observed geocenter motion from precise orbit determination of GRACE satellites using GPS tracking and accelerometer data
- 267 Downloads
We present a method to estimate geocenter motion through single low-earth orbiter (LEO) precise orbit determination (POD) using global positioning system (GPS) tracking data and accelerometer data from the GRACE satellites. We fix the values of the GPS ephemerides and time-varying clock offsets to precise estimates from the definitive constellation product produced by the Jet Propulsion Laboratory. As part of the POD process of the LEOs, we estimate a translation of the reference coordinate system realized by the GPS orbit and clock product. Doing so accounts for the inconsistency between the Earth’s center of mass coordinate system used for the orbit integration of the LEOs, and the terrestrial reference frame produced by the GPS orbit and clock product. The resulting translation parameters estimated separately from the GRACE-A and GRACE-B satellites show very similar variations from day to day. They represent the geocenter motion, as realized from the difference between the origin of the terrestrial reference frame represented by the GPS orbit and clock product and the Earth’s instantaneous center of mass defined by the GRACE satellite dynamical orbital motion. Comparisons with geocenter motion observations from other techniques show that our daily estimates of geocenter motion agree well, when smoothed, in both the amplitude and phase of the annual signal. This validates both the high sensitivity of the GRACE GPS measurement type to geocenter motion and the high precision of the GRACE force model enabled by accelerometer measurements, the two essential components for estimation of geocenter motion with this technique.
KeywordsGeocenter GRACE GPS
The work described in this paper is carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We thank Xiaoping Wu for providing the data of unified inverse results. The data of monthly SLR solutions are from The University of Texas at Austin Center for Space Research (ftp://csr.utexas.edu/pub/slr/geocenter), while weekly SLR solutions are from the Astronomical Institute of the University of Bern (ftp://ftp.aiub.unibe.ch/GRAVITY/GEOCENTER/GEOC_SLR.GCC). We also thank the Editor-in-Chief and the three anonymous reviewers for their constructive comments and suggestions.
Da Kuang formulated the algorithm, processed the data, and drafted the article. Willy Bertiger developed the analysis tools to enable dynamic GRACE POD using accelerometer data for this study. Shailen Desai conceived the plan to determine the time-varying gravity simultaneously to separate the largest perturbing force and provided inputs to the article. Bruce Haines performed research on the error in reference frame dissemination through GPS products, validated the results and provided inputs to the article. Dah-Ning Yuan performed research on various parameterizations for dynamic GRACE POD using accelerometer data.
- Bar-Sever Y, Haines B, Kuang D, Nerem S (2012) Geodetic reference antenna in space (GRASP): status and simulations. In: AGU fall meeting, San Francisco, 3–7 Dec 2012Google Scholar
- Bertiger W, Bar-Sever Y, Bettadpur S, Dunn C, Haines B, Kruizinga G, Kuang D, Nandi S, Romans L, Watkins M, Wu S (2002) GRACE: millimeters and microns in orbit. In: Proceedings of ION GPS 2002, Portland, OR, 24–27 Sept 2002, pp 2022–2029Google Scholar
- Cheng MK, Ries JC, Tapley BD (2013) Geocenter variations from analysis of SLR data, in reference frames for applications in geosciences. In: International association of geodesy symposia, vol 138. Springer, Berlin, pp 19–26Google Scholar
- Haines B, Bar-Sever Y, Bertiger W, Desai S, Harvey N, Weiss J (2011) A GPS-based terrestrial reference frame from a combination of terrestrial and orbiter data. In: AGU fall meeting, San Francisco, Dec 2011Google Scholar
- Kuang D, Desai S, Haines B, Sibthorpe A (2014) Orbital accelerometry by LEO GNSS tracking: theory and practice. In: Proceeding of the ION GNSS + 2014, Tampa, Florida, 8–12 Sept 2014, pp 1524–1535Google Scholar