scholarly journals DIONYSOS SATELLITE OBSERVATORY AND HIGHER GEODESY LABORATORY: HISTORY AND PERSPECTIVES

2017 ◽  
Vol 50 (2) ◽  
pp. 1091
Author(s):  
A. Marinou ◽  
D. Anastasiou ◽  
X. Papanikolaou ◽  
D. Paradissis ◽  
V. Zacharis
Keyword(s):  
Gravity Field ◽  
Temporal Variations ◽  
Technological Advance ◽  
Satellite Geodesy ◽  
Research Needs ◽  
Reference Systems ◽  
Earth’S Gravity Field ◽  
Wide Range

Dionysos Satellite Observatory and Higher Geodesy Laboratory have been in operation since the 60s and their main objective is to fulfill academic and research needs, determined through the ongoing scientific and technological advance in the field of geodesy. They are involved in all scientific domains related to the determination of earth’s size and figure, as well as its temporal variations. Their field of expertise is Satellite Geodesy, (spanning a wide range of applications like reference systems, tectonic geodesy, etc.), as well as the study of the geoid and earth's gravity field.

Determination of Polar Motion and Earth Rotation from Laser Tracking of Satellites

1979 ◽  
Vol 82 ◽  
pp. 231-238 ◽  
Author(s):  
David E. Smith ◽  
Ronald Kolenkiewicz ◽  
Peter J. Dunn ◽  
Mark Torrence
Keyword(s):  
Gravity Field ◽  
Radiation Pressure ◽  
Orbit Determination ◽  
Earth Rotation ◽  
Polar Motion ◽  
Ocean Tides ◽  
Earth’S Gravity Field ◽  
Laser Tracking ◽  
Order Of Magnitude

Laser tracking of the Lageos spacecraft has been used to derive the position of the Earth's pole of rotation at 5-day intervals during October, November and December 1976. The estimated precision of the results is 0.01 to 0.02 arcseconds in both x and y components, although the formal uncertainty is an order of magnitude better, and there is general agreement with the Bureau International de l'Heure smoothed pole path to about 0.02 arcseconds. Present orbit determination capability of Lageos is limited to about 25 cm rms fit to data over periods of 5 days and about 50 cm over 50 days. The present major sources of error in the perturbations of Lageos are Earth and ocean tides followed by the Earth's gravity field, and solar and Earth reflected radiation pressure. Ultimate accuracy for polar motion and Earth rotation from Lageos after improved modeling of the perturbing forces appears to be of order ± 5 cm for polar motion over a period of about 1 day and about ± 0.2 to ± 0.3 milliseconds in U.T. for periods up to 2 or 3 months.

scholarly journals An improved test of the general relativistic effect of frame-dragging using the LARES and LAGEOS satellites

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
Ignazio Ciufolini ◽  
Antonio Paolozzi ◽  
Erricos C. Pavlis ◽  
Giampiero Sindoni ◽  
John Ries ◽  
...  
Keyword(s):  
General Relativity ◽  
Gravity Field ◽  
Temporal Variations ◽  
Gravity Field Model ◽  
Earth’S Gravity Field ◽  
Frame Dragging ◽  
Earth Gravity ◽  
Gravity Field Determination ◽  
General Relativistic ◽  
Static Part

Abstract We report the improved test of frame-dragging, an intriguing phenomenon predicted by Einstein’s General Relativity, obtained using 7 years of Satellite Laser Ranging (SLR) data of the satellite LARES (ASI, 2012) and 26 years of SLR data of LAGEOS (NASA, 1976) and LAGEOS 2 (ASI and NASA, 1992). We used the static part and temporal variations of the Earth gravity field obtained by the space geodesy mission GRACE (NASA and DLR) and in particular the static Earth’s gravity field model GGM05S augmented by a model for the 7-day temporal variations of the lowest degree Earth spherical harmonics. We used the orbital estimator GEODYN (NASA). We measured frame-dragging to be equal to $$0.9910 \pm 0.02$$0.9910±0.02, where 1 is the theoretical prediction of General Relativity normalized to its frame-dragging value and $$\pm 0.02$$±0.02 is the estimated systematic error due to modelling errors in the orbital perturbations, mainly due to the errors in the Earth’s gravity field determination. Therefore, our measurement confirms the prediction of General Relativity for frame-dragging with a few percent uncertainty.

scholarly journals The significance of determination of the absolute value of gravity in geodesy

Tehnika ◽  
2021 ◽  
Vol 76 (1) ◽  
pp. 17-24
Author(s):  
Sofija Naod
Keyword(s):  
Theoretical Basis ◽  
Absolute Gravity ◽  
Reference Systems ◽  
Global Knowledge ◽  
Earth’S Gravity Field ◽  
Absolute Value ◽  
Reference Networks ◽  
The Absolute ◽  
Gravimetric System

The gravity is used to solve geodesy's primary tasks, such as determining geoid and defining the height and gravimetric reference networks of different scales, from national to global. Knowledge of gravity is of great importance for both metrology and geodetic metrology. In addition to the historical overview of absolute gravimeters, this paper presents the theoretical basis of the most commonly used method for determining the absolute value of gravity. The principle of operation of the absolute gravimeter FG5 and the importance of international comparison of absolute gravimeters are briefly presented. An overview of the gravimetric reference systems is given, emphasizing the establishment of the International Reference Gravimetric System. The previous works concerning the absolute determination of acceleration due to Earth's gravity field in Serbia are presented. Finally, the importance of determining the absolute value of gravity from the geodetic and metrological perspective is pointed out. Both national and international significance of determining absolute gravity in defining gravimetric reference systems and the importance of absolute gravity in monitoring global phenomena are emphasized.

scholarly journals Lithospheric stress, strain and displacement changes from GRACE-FO time-variable gravity: case study for Sar-e-Pol Zahab Earthquake 2018

2020 ◽  
Vol 223 (1) ◽  
pp. 379-397
Author(s):  
Mehdi Eshagh ◽  
Farzam Fatolazadeh ◽  
Robert Tenzer
Keyword(s):  
Gravity Field ◽  
Elastic Shell ◽  
Lower Boundary ◽  
Stable Solution ◽  
Temporal Variations ◽  
Stress Strain ◽  
Satellite Gravity ◽  
Earth’S Gravity Field ◽  
Long Wavelength ◽  
Ill Posed

SUMMARY Temporal variations in the Earth's gravity field can be used for monitoring of lithospheric deformations. The network of continuously operating gravity stations is required for this purpose but a global coverage by such network is currently extremely sparse. Temporal variations in long-wavelength part of the Earth's gravity field have been, however, observed by two satellite missions, namely the Gravity Recovery And Climate Experiment (GRACE) and the GRACE Follow-On (GRACE-FO). These satellite gravity observations can be used to study long-wavelength deformations of the lithosphere. Consequently, considering the lithosphere as a spherical elastic shell and solving the partial differential equation of elasticity for it, the stress, strain and displacement inside the lithosphere can be estimated. The lower boundary of this shell is assumed to be stressed by mantle convection, which has a direct relation to the Earth's gravity field according to Runcorn's theory. Changes in gravity field lead to changes in the sublithospheric stress and the stress propagated throughout the lithosphere. In this study, we develop mathematical models in spherical coordinates for describing the stress propagation from the sublithosphere through the lithosphere. We then organize a system of observation equations for finding a special solution to the boundary-value problem of elasticity in the way that provides a stable solution. In contrast, models presented in previously published studies are ill-posed. Furthermore, we use constants of the solution determined from the boundary stresses to determine the strain and displacements leading to these stresses, while in previous studies only the stress has been considered according to rheological properties of the lithosphere. We demonstrate a practical applicability of this theoretical model to estimate the stress–strain redistribution caused by the Sar-e-Pol Zahab 2018 earthquake in Iran by using the GRACE-FO monthly solutions.

scholarly journals ANALYSIS OF ISOSTATICALLY-BALANCED CORTICAL MODELS USING MODERN GLOBAL GEOPOTENTIAL MODELS

2017 ◽  
Vol 23 (4) ◽  
pp. 623-635
Author(s):  
Claudia Infante ◽  
Claudia Tocho ◽  
Daniel Del Cogliano
Keyword(s):  
Gravity Field ◽  
Temporal Variations ◽  
Geoid Height ◽  
Geological Structure ◽  
Earth’S Gravity Field ◽  
Isostatic Equilibrium ◽  
Geopotential Models ◽  
Show Evidence ◽  
Residual Geoid ◽  
Cortical Models

Abstract: The knowledge of the Earth's gravity field and its temporal variations is the main goal of the dedicated gravity field missions CHAMP, GRACE and GOCE. Since then, several global geopotential models (GGMs) have been released. This paper uses geoid heights derived from global geopotential models to analyze the cortical features of the Tandilia structure which is assumed to be in isostatic equilibrium. The geoid heights are suitably filtered so that the structure becomes apparent as a residual geoid height. Assuming that the geological structure is in isostatic equilibrium, the residual geoid height can be assimilated and compared to the isostatic geoid height generated from an isostatically compensated crust. The residual geoid height was obtained from the EGM2008 and the EIGEN-6C4 global geopotential models, respectively. The isostatic geoid was computed using the cortical parameters from the global crustal models GEMMA and CRUST 1.0 and from local parameters determined in the area under study. The obtained results make it clear that the isostatic geoid height might become appropriate to validate crustal models if the structures analyzed show evidence of being in isostatic equilibrium.

Development of a simulator of a satellite-to-satellite interferometer for determination of the Earth’s gravity field

2005 ◽  
Vol 76 (12) ◽  
pp. 124501 ◽  
Author(s):  
Shigeo Nagano ◽  
Mizuhiko Hosokawa ◽  
Hiroo Kunimori ◽  
Taizoh Yoshino ◽  
Seiji Kawamura ◽  
...  
Keyword(s):  
Gravity Field ◽  
Earth’S Gravity Field
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