Determination of Seasonal Variations of Low-Degree Earth Gravity Field from CHAMP Geometric Orbits

Based on satellite dynamics, 1 year’s CHAMP geometric precise orbit data are used in this paper to fit the satellite orbits by Cowell II numerical integral and partitioned Bayesian least square parameter estimation. Time series of low degree geopotential coefficients and are respectively calculated, which reflects obviously seasonal variations of and . The results / month, /month indicate the geodynamical shape of the earth is getting rounder and rounder and at the same time its pear-shaped component adds gradually.

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Effect of the Gravitational Aberration on the Earth Gravity Field

Artificial Satellites ◽

10.2478/arsa-2021-0001 ◽

2021 ◽

Vol 56 (1) ◽

pp. 1-9

Author(s):

Janusz B. Zieliński ◽

Vladimir V. Pashkevich

Keyword(s):

Gravity Field ◽

Orbit Determination ◽

Artificial Satellites ◽

Finite Speed ◽

Earth Gravity Field ◽

Earth Gravity ◽

The Earth ◽

First Approximation ◽

Classic Theory

Abstract Discussing the problem of the external gravitational potential of the rotating Earth, we have to consider the fundamental postulate of the finite speed of the propagation of gravitation. This can be done using the expressions for the gravitational aberration compared to the Liénard–Wiechert solution of the retarded potentials. The term gravitational counter-aberration or co-aberration is introduced to describe the pattern of the propagation of the gravitational signal emitted by the rotating Earth. It is proved that in the first approximation, the classic theory of the aberration of light can be applied to calculate this effect. Some effects of the gravitational aberration on the external gravity field of the rotating Earth may influence the orbit determination of the Earth artificial satellites.

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Proposals for an Improved Nutation Formula

Symposium - International Astronomical Union ◽

10.1017/s0074180900086575 ◽

1990 ◽

Vol 141 ◽

pp. 148-148

Author(s):

E. Groten ◽

S. Y. Zhu

Keyword(s):

Gravity Field ◽

Ocean Tide ◽

Combined Model ◽

Earth Gravity ◽

The Earth ◽

Low Degree ◽

Vlbi Data ◽

Nutation Series ◽

New Formula

There are a variety of reasons why in geodesy an improved formula for nutation is needed; related topics of interest are the determination of time-dependences in low degree zonals of the earth gravity field, ocean tide modeling, determination of odd harmonics of gravity field etc. in satellite geodesy. A combined model of deterministic and stochastic components is used in order to evaluate two new nutation series where, in an adjustment, mainly VLBI data (IRIS, GSFC, IERS) have been applied. Contrary to earlier revisions of the present nutation formula, not only the five significantly affected waves (annual, semi-annual, FCN etc.) are corrected but rather all constituents are revised in such a way that white noise residuals result from the adjusted observations, based on the new formula. Still remaining problems (such as the separation of long-period terms from precession etc.) are outlined.

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The Optimum Conventional Terrestrial System Determined by VLBI and SLR Stations

Symposium - International Astronomical Union ◽

10.1017/s0074180900086460 ◽

1990 ◽

Vol 141 ◽

pp. 118-118

Author(s):

W. Kosek ◽

B. Kolaczek

Keyword(s):

North America ◽

Earth Rotation ◽

High Accuracy ◽

Earth Gravity Field ◽

Terrestrial System ◽

Earth Gravity ◽

The Earth ◽

Station Coordinates ◽

The World

The optimum Conventional Terrestrial System (CTS) can be defined by accurate coordinates of some number of stations distributed homogeneously all over the world. There are scores of laser and VLBI stations whose coordinates are known with high accuracy of the order of 1-2 cm. There are many CTS defined by the sets of station coordinates determined in the process of determination of the Earth rotation paramaters and the Earth gravity field. Presently existing stations are not distributed homogeneously on the Earth. They are located mostly in Europe and in North America. In this situation, the errors of orientation of axes and origin positions are not equal. Some of them, based on a small number of not homogeneously distributed stations, are not well-defined (stable).

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