Analysis of Systematic Errors in Geocenter Coordinates Determined From GNSS, SLR, DORIS, and GRACE

Abstract

The goal of this paper is to determine and analyze the common geocenter signal from the geocenter coordinates based on four independent techniques: Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), Global Navigation Satellite System (GNSS), Gravity Recovery And Climate Experiment with the ocean bottom pressure model, and Satellite Laser Ranging, and to analyze the residuals as the differences between these geocenter coordinates and their common signal. Another objective of this paper is to compute variable amplitudes and phases of the annual and semi-annual oscillations in the geocenter coordinates of these techniques by the combination of the Fourier Transform Band Pass Filter (FTBPF) with the Hilbert Transform (FTBPF + HT) and to compare their mean values with those obtained by other authors. It was assumed that the geocenter time series of individual techniques consist of the common signal of geocenter motion, systematic errors resulting from orbital modeling and noise. Generally, the annual oscillation amplitudes in these techniques computed by the FTBPF + HT vary in time and their mean values are of the order of 2 mm for the X coordinate, 2.4–3.6 mm for the Y coordinate and 2.8–5.6 mm for the Z coordinate and the semi-annual oscillation amplitude is variable and about two times smaller than the annual one. The phases of these two oscillations are also variable, there are differences in their mean values for different techniques and the semi-annual oscillation phases changes throughout the entire phase range. To detect the common geocenter signal the wavelet-based semblance filtering (WBSF) method was applied. The weighted mean model was computed from all geocenter coordinate pairs from individual techniques assuming weights as inversely proportional to the variances of differences between the geocenter coordinates and their corresponding WBSF outputs. The average and median models computed from these outputs show a good agreement with the weighted mean model and generally, the average amplitudes of the annual signal in these models are of the order of 2 mm in each geocenter coordinate. The FTBPF amplitude spectra of these models reveals the retrograde annual oscillation in the XY equatorial plane. The FTBPF and FTBPF + HT amplitude spectra of geocenter time series and their residuals show mainly the maxima of different heights in the annual frequency band. The annual oscillations left in all residuals and oscillations with period less than ~ 120 days in DORIS and GNSS amplitude spectra may be caused by systematic errors of techniques resulting from mis-modeling of satellite orbits.

Geocenter coordinates derived from multi-GNSS: a look into the role of solar radiation pressure modeling

“…This movement is expressed by a three-dimensional vector known as geocenter coordinates (GCC). Although the essence of the geocenter motion is straightforward, the direct observation of its instantaneous location is one of the most demanding applications of highprecision geodetic techniques and has a profound impact on the geophysical interpretation of geodetic measurements (Blewitt 2015;Kosek et al 2020).…”

Interannual and Intra-seasonal Oscillations in the Length of Day, Atmospheric Angular Momentum and Atmospheric Surface Pressure Time Series Observed at Chosen Meteorological Stations Near the Equator

“…is the parabolic transmittance function in which λ is half of the window bandwidth and  is the frequency argument. The variable amplitudes and phases of the broadband oscillations can be computed by the FTBPF+HT combination (Kosek et al, 2015(Kosek et al, , 2020:…”

Geocenter motions derived from BDS observations: Effects of the solar radiation pressure model and constellation configuration

“…Since the ITRF origin follows the mean CM linearly with time, the origin of ITRF is consistent with CM on a secular timescale but with CF on a short timescale (Dong et al 2003;Collilieux et al 2009), and the vector offset of CM relative to CF is known as the geocenter coordinates (GCC). Precise determination of the instantaneous GCC is one of the critical tasks of geodesy and has a profound impact on the interpretation and application of the ITRF (Wu et al 2012;Blewitt 2015;Zannat et al 2017;Kosek et al 2020).…”

“…However, the Z component of GNSS-derived GCC suffers from modeling deficiencies and collinearity problems in solar radiation pressure (SRP) modeling, tropospheric delay and clock offset estimation, and phase ambiguity fixing, leading to the spurious signals in GCC-Z series. (Meindl et al 2013;Rebischuang et al 2014;Kosek et al 2020).…”