Geocenter Variations from Analysis of SLR Data
The Earth’s center of mass (CM) is defined in the satellite orbit dynamics as the center of mass of the entire Earth system, including the solid earth, oceans, cryosphere and atmosphere. Satellite Laser Ranging (SLR) provides accurate and unambiguous rang
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Geocenter Variations from Analysis of SLR Data M.K. Cheng, J.C. Ries, and B.D. Tapley
Abstract
The Earth’s center of mass (CM) is defined in the satellite orbit dynamics as the center of mass of the entire Earth system, including the solid earth, oceans, cryosphere and atmosphere. Satellite Laser Ranging (SLR) provides accurate and unambiguous range measurements to geodetic satellites to determine variations in the vector from the origin of the ITRF to the CM. Estimates of the Global mass redistribution induced geocenter variations at seasonal scales from SLR are in good agreement with the results from the global inversion from the displacements of the dense network of GPS sites and from ocean bottom pressure model and GRACE-derived geoid changes. Keywords
Geocenter Satellite laser ranging (SLR) Center of mass
1
Introduction
The Terrestrial Reference System (TRS) is a fundamental concept for all studies in the geosciences, and it is of critical importance for satellite navigation and other geoinformation applications. The Earth’s center of mass (CM or geocenter) is the center of mass of the entire Earth system, including the solid earth, oceans, cryosphere surface water and atmosphere. The CM is the point about which any Earth satellite will orbit and can be determined from observations of an Earth-orbiting satellite motion. The origin of the International Terrestrial Reference Frame (ITRF) is currently derived from long-term analysis of Satellite Laser Ranging (SLR) data, but its dynamic tie to the CM is not yet a component of the conventional model of ITRF. The variation of the CM with respect to the origin of ITRF is known as the geocenter motion and reflects the global scale mass redistribution and the interaction between the solid Earth and the mass loading. Determination of the Earth’s center of mass is
an important component for the realization of the Terrestrial Reference System, and has attracted considerable attention; see for example Trupin et al. (1992), Dong et al. (1997), Watkins and Eanes (1997), Pavlis (2002), Angermann and Mu¨ller (2008), Pavlis and Kusmicz-Cieslak (2009), and those papers that contributed to the IERS Analysis Campaign to Investigate Motions of Geocenter (Ray 1999). In this study, the geocenter motion is simultaneously estimated along with the low-degree portion of the gravity field, providing a unified recovery of the signals in the SLR data. This paper discusses the analysis of estimates of the annual geocenter variations from a multi-satellite SLR data set and compares the results with the ILRS SLR network translation solutions (Collilieux et al. 2009; Altamimi et al. 2010) based on the International Laser Ranging Service (ILRS; Pearlman et al. 2002) and the global inversion mostly based on the 3-dimensional displacement of GPS stations (Wu et al. 2010a).
2 M.K. Cheng (*) J.C. Ries B.D. Tapley Center for Space Research, University of Texas at Austin, Austin, TX 78759-5321, USA e-mail: [email protected]
Theory
The Earth’s gravitational potential is expressed
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