A high‐quality global gravity field model from CHAMP GPS tracking data and accelerometry (EIGEN‐1S)
Christoph ReigberG. BalminoP. SchwintzerR. BiancaleAlbert BodeJean‐Michel LemoineRolf KönigSylvain LoyerH. NeumayerJean‐Charles MartyFranz BarthelmesF. PérosanzShen Yuan Zhu
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Abstract:
Using three months of GPS satellite‐to‐satellite tracking and accelerometer data of the CHAMP satellite mission, a new long‐wavelength global gravity field model, called EIGEN‐1S, has been prepared in a joint German‐French effort. The solution is derived solely from analysis of satellite orbit perturbations, i.e. independent of oceanic and continental surface gravity data. EIGEN‐1S results in a geoid with an approximation error of about 20 cm in terms of 5 × 5 degree block mean values, which is an improvement of more than a factor of 2 compared to pre‐CHAMP satellite‐only gravity field models. This impressive progress is a result of CHAMP's tailored orbit characteristics and dedicated instrumentation, providing continuous tracking and direct on‐orbit measurements of non‐gravitational satellite accelerations.Keywords:
Orbit Determination
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The spatial resolution of the earth's gravity field for the future GRACE Follow-On is discussed by analyzing the spatial disturbance gravity spectrum and the accumulative geoid error spectrum.The radial disturbance gravity with the height 200 km and 250 km is computed,using the EGM96 gravitational field model.Analyzing the radial gravity disturbance spectrum characteristics,a new earth's gravity field model of 281 and 242 degrees can be recovered at the two orbit heights.The accumulative geoid error spectrum model is given,and the accumulative geoid error spectrum at the height of 200 km and 250 km is computed.Analyzing the accumulative geoid error,it can be concluded that the earth's gravity field can be recovered to a degree of 286 and 228.
Gravity of Earth
Free-air gravity anomaly
Gravimetry
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An analysis of current static and time-variable gravity field models is presented focusing on the medium to high frequencies of the geopotential as expressed by the spherical harmonic coefficients. A validation scheme of the gravity field models is implemented based on dynamic orbit determination that is applied in a degree-wise cumulative sense of the individual spherical harmonics. The approach is applied to real data of the Gravity Field and Steady-State Ocean Circulation (GOCE) and Gravity Recovery and Climate Experiment (GRACE) satellite missions, as well as to GRACE inter-satellite K-band ranging (KBR) data. Since the proposed scheme aims at capturing gravitational discrepancies, we consider a few deterministic empirical parameters in order to avoid absorbing part of the gravity signal that may be included in the monitored orbit residuals. The present contribution aims at a band-limited analysis for identifying characteristic degree ranges and thresholds of the various GRACE- and GOCE-based gravity field models. The degree range 100–180 is investigated based on the degree-wise cumulative approach. The identified degree thresholds have values of 130 and 160 based on the GRACE KBR data and the GOCE orbit analysis, respectively.
Geopotential
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Orbit Determination
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Geopotential
Collocation (remote sensing)
Least-squares function approximation
Gravimetry
Gravity of Earth
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In this paper we formulate the boundary-value problem for the determination of the gravimetric geoid considering a satellite gravitational model as a reference. We show that the long-wavelength part of the gravitational field generated by topographical masses must be added to the satellite model in order to prescribe a reference gravitational potential for a partly internal and partly external problem for geoid determination. We choose a reference potential that does not depend on the way topographical masses are compensated or condensed, but only on the satellite reference model and on the difference of gravitational potentials induced by topographical masses in the spaces outside the Earth and below the geoid. The latter contribution to the reference potential is expressed in the form of an ellipsoidal harmonic series, and the expansion coefficients are tabulated numerically up to degree 20.
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