Earth’s gravity from space

Rummel, Reiner

doi:10.1007/s12210-020-00889-8

Cited by 6 publications

(5 citation statements)

References 74 publications

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“…The following is a very brief summary of some results of the geophysical, oceanographic and geodetic use of GOCE. Reference is made to Rummel (2020). Gravity or geoid anomalies are a measure for the imbalance of the Earth masses in the crust, lithosphere and upper mantle (Alvarez et al 2014;Bouman et al 2016;Braitenberg 2015;Ebbing et al 2014;v/d Meijden et al 2015;Panet et al 2014).…”

Section: Scientific Resultsmentioning

confidence: 99%

Satellite Gravimetry: A Review of Its Realization

et al. 2021

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Since Kepler, Newton and Huygens in the seventeenth century, geodesy has been concerned with determining the figure, orientation and gravitational field of the Earth. With the beginning of the space age in 1957, a new branch of geodesy was created, satellite geodesy. Only with satellites did geodesy become truly global. Oceans were no longer obstacles and the Earth as a whole could be observed and measured in consistent series of measurements. Of particular interest is the determination of the spatial structures and finally the temporal changes of the Earth's gravitational field. The knowledge of the gravitational field represents the natural bridge to the study of the physics of the Earth's interior, the circulation of our oceans and, more recently, the climate. Today, key findings on climate change are derived from the temporal changes in the gravitational field: on ice mass loss in Greenland and Antarctica, sea level rise and generally on changes in the global water cycle. This has only become possible with dedicated gravity satellite missions opening a method known as satellite gravimetry. In the first forty years of space age, satellite gravimetry was based on the analysis of the orbital motion of satellites. Due to the uneven distribution of observatories over the globe, the initially inaccurate measuring methods and the inadequacies of the evaluation models, the reconstruction of global models of the Earth's gravitational field was a great challenge. The transition from passive satellites for gravity field determination to satellites equipped with special sensor technology, which was initiated in the last decade of the twentieth century, brought decisive progress. In the chronological sequence of the launch of such new satellites, the history, mission objectives and measuring principles of the missions CHAMP, GRACE and GOCE flown since 2000 are outlined and essential scientific results of the individual missions are highlighted. The special features of the GRACE Follow-On Mission, which was launched in 2018, and the plans for a next generation of gravity field missions are also discussed.

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Section: Scientific Resultsmentioning

confidence: 99%

Satellite Gravimetry: A Review of Its Realization

et al. 2021

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“…Moreover, when the remove-compute-restore (RCR) method is combined with a smoothing topo-graphic correction like in the Helmert's condensation or RTM methods, the Stokes' integral's numerical quadrature may be evaluated on reduced and smoother gravity anomalies than when a global equipotential surface is used. Analysis of the temporal variations of the gravity field, combined with the time series of monthly gravity models, will lead to an improved understanding of the various compartments of the climate system (atmosphere, oceans, terrestrial water, continental crust and lithosphere) (Rummel, 2020), and provide a valuable data source for time-variable gravity studies, such as climate change.…”

Section: Introductionmentioning

confidence: 99%

A level Ellipsoid for modelling regional Gravity Field

Chivatsi,

Md,

Pa'suya

2023

Preprint

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Modern, very precise gravity models are now being created in the discipline of geodesy, using purely satellite techniques. Thanks to the GOCE and GRACE missions, high quality global gravitational models have been computed and made available to users. The models allow for the derivation of gravity field functionals when coupled with reference equipotential normal ellipsoids, such as GRS80 and WGS84. These ellipsoids represent the global fit to the geoid, but may depart from the geoid in local circumstances. The precision of computed gravimetric field functionals depends on the fit of the reference model to the geoid. In this study, a regional normal ellipsoid that fits the local geoid is computed from terrestrial data, using both ordinary and combined least squares optimization techniques, applying the theory of equipotential ellipsoid. Results from the combined model were used to compute the geometrical and physical constants of the new ellipsoid A normal ellipsoid, with semi-major axis of 6378145.549089m and flattening, 269.792502072 and the same mass and angular velocity as the earth was obtained. These parameters can be used with a geopotential model to yield smoother gravity field functionals, for use in geoid modelling and other geoscience applications.

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“…The Earth's gravity model plays a crucial in studying space satellite orbit (Rummel, 2020). As described by (Barthelmes, 2013) In which: V is the gravitational potential; r, φ, and λ correspond to the spherical geocentric coordinates of the computation point (radius, latitude, and longitude); R is a reference radius, usually taken as the mean semi-major axis of Earth in geodesy; GM is the gravitational constant times the mass of the Earth; l and m are degree and order of spherical harmonic, lmax is the maximum degree of the model expansion; 𝑃 ̅ 𝑙𝑚 are fully normalized Legendre polynomials of degree l and order m, and 𝐶 ̅ 𝑙𝑚 and 𝑆 ̅ 𝑙𝑚 are spherical harmonic coefficients.…”

Section: Introductionmentioning

confidence: 99%

Effect of the low-order coefficients of the Earth gravity model in calculating the satellite orbit

Luong,

Tran

2023

JMES

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The Earth's gravity model is a crucial factor in determining satellite orbits. Scientific organizations such as GFZ Potsdam in Germany, GRGS Toulouse in France, and AIUB in Switzerland have established Earth gravity models with increasing precision of spherical harmonic coefficients. Low-order coefficients, including C ̅_21,( S) ̅_21, C ̅_10,C ̅_11,( S) ̅_11and C ̅_20, play a vital role in describing changes in the Earth's poles, geometric center, and flattening. To evaluate the impact of these coefficients and understand altimeter satellite orbital error, the Propagerror program was developed. This program calculates satellite orbital error from the differential components of Earth gravity model spherical harmonic coefficients (dC/Slm), which can be obtained from the difference between two gravity models or from seasonal and annual components of spherical harmonics. By separating appropriate low-order components in the Earth gravity models, the Propagerror program enables the estimation of satellite orbital error. In this study, we isolate C ̅_10,C ̅_11,( S) ̅_11, and C ̅_21,( S) ̅_21 coefficients in the EIGEN-GRGS.RL02bis.MF and EIGEN-6S gravity models to assess the geophysical impact on satellite orbits. The influence of the geometry center elements results in a 2 cm error in the Jason-2 satellite, while the rotational axis elements have no effect. The C ̅_31,( S) ̅_31 coefficient has a 6-7 mm impact on the accuracy of the Jason-2 satellite, as demonstrated by the satellite error map in two situations with and without the C ̅_31,( S) ̅_31 harmonic coefficient. This study highlights the significance of regulating function coefficients in satellite orbit determination, particularly the low-level harmonic parameters. The Propagerror program provides insights into the impact of each spherical harmonic parameter on satellite orbits, contributing to the improvement of orbit accuracy and the understanding of the Earth's gravity model.

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Earth’s gravity from space

Cited by 6 publications

References 74 publications

Satellite Gravimetry: A Review of Its Realization

Satellite Gravimetry: A Review of Its Realization

A level Ellipsoid for modelling regional Gravity Field

Effect of the low-order coefficients of the Earth gravity model in calculating the satellite orbit

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