17:30 〜 17:45
[G01-4-05] Non-linear Geocenter Motion from Multi-Technique Geocentric Station Coordinate Time Series in a Terrestrial Reference Frame on Dynamic Earth and GRACE Gravity Data
Spherical harmonic expansions of Earth's surface mass variations start from three degree-1 terms. These induce geocenter motion between the center-of-mass of the total Earth system (CM) and the center-of-figure of the solid Earth surface (CF), as well as a degree-1 surface deformation field. However, GRACE's K-band ranging data system is not sensitive to these variation modes. For complete spectral coverage and robust assessment of geographic mass budget using GRACE data, very accurate knowledge of geocenter motion is required but difficult to obtain.
To address the ever-changing nature of the solid Earth surface, recently, an experimental Kalman filter and time series terrestrial reference frame (KALREF) has been realized by a collaborative effort of JPL and IGN to determine nearly instantaneous geocentric station coordinates of all 4 space geodetic techniques. Through local tie measurements and co-motion constraints, satellite laser ranging (SLR)'s CM sensitivity is transferred to other technique networks, and SLR's many data gaps are bridged by co-located dense GPS data. For geocenter motion determination, we use a new unified approach by combining KALREF geocentric displacements of a larger and better-distributed 82-site network with GRACE gravity data. Both translational and deformational signatures will be exploited for retrieval of the degree-1 surface mass variation coefficients. Higher degree terms are estimated simultaneously using GRACE gravity data, which further improves CF knowledge and reduces aliasing effects. Such a data combination also uses full covariance matrices of all data types to facilitate a reliable variance component estimation. The combination of the 82-station KALREF coordinate time series with GRACE improved the precisions of non-linear geocenter motion components by factors of 2 to 3 compared with those obtained from the combination of SLR and GRACE.
To address the ever-changing nature of the solid Earth surface, recently, an experimental Kalman filter and time series terrestrial reference frame (KALREF) has been realized by a collaborative effort of JPL and IGN to determine nearly instantaneous geocentric station coordinates of all 4 space geodetic techniques. Through local tie measurements and co-motion constraints, satellite laser ranging (SLR)'s CM sensitivity is transferred to other technique networks, and SLR's many data gaps are bridged by co-located dense GPS data. For geocenter motion determination, we use a new unified approach by combining KALREF geocentric displacements of a larger and better-distributed 82-site network with GRACE gravity data. Both translational and deformational signatures will be exploited for retrieval of the degree-1 surface mass variation coefficients. Higher degree terms are estimated simultaneously using GRACE gravity data, which further improves CF knowledge and reduces aliasing effects. Such a data combination also uses full covariance matrices of all data types to facilitate a reliable variance component estimation. The combination of the 82-station KALREF coordinate time series with GRACE improved the precisions of non-linear geocenter motion components by factors of 2 to 3 compared with those obtained from the combination of SLR and GRACE.