Recovering the global gravitational field from satellite measurements of the full gravity gradient

2000 ◽  
pp. 63-67 ◽  
Author(s):  
M. S. Petrovskaya ◽  
J. B. Zieliński
Keyword(s):  
Gravitational Field ◽  
Gravity Gradient ◽  
Satellite Measurements

MULTI-SCALE MECHANICAL BEHAVIOR ANALYSIS ON FLUID–SOLID COUPLING FOR OSTEONS IN VARIOUS GRAVITATIONAL FIELDS

2021 ◽  
Author(s):  
HAO ZHANG ◽  
HAI-YING LIU ◽  
CHUN-QIU ZHANG ◽  
ZHEN-ZHONG LIU ◽  
WEI WANG
Keyword(s):  
Gravitational Field ◽  
Fluid Shear Stress ◽  
Bone Matrix ◽  
Fluid Pressure ◽  
Gravity Gradient ◽  
Static Compression ◽  
Gravitational Fields ◽  
Multi Scale ◽  
Earth’S Gravitational Field ◽  
Mechanical Microenvironment

Background: Compact bone mainly consists of cylindrical osteon structures. In microgravity, the change in the mechanical microenvironment of osteocytes might be the root cause of astronauts’ bone loss during space flights. Methods: A multi-scale three-dimensional (3D) fluid–solid coupling finite element model of osteons with a two-stage pore structure was developed using COMSOL software based on the natural structure of osteocytes. Gradients in gravitational fields of [Formula: see text]1, 0, 1, 2.5, and 3.7[Formula: see text]g were used to investigate the changes in the mechanical microenvironment on osteocyte structure. The difference in arteriole pulsating pressure and static compression stress caused by each gravity gradient was investigated. Results: The mechanical response of osteocytes increased with the value of g, compared with the Earth’s gravitational field. For instance, the fluid pressure of osteocytes and the von Mises stress of bone matrix near lacunae decreased by 31.3% and 99.9%, respectively, in microgravity. Under static loading, only about 16.7% of osteocytes in microgravity and 58.3% of osteocytes in the Earth’s gravitational field could reach the fluid shear stress threshold of biological reactions in cell culture experiments. Compared with the Earth’s gravitational field, the pressure gradient inside osteocytes severely decreased in microgravity. Conclusion: The mechanical microenvironment of osteocytes in microgravity might cause significant changes in the mechanical microenvironment of osteocytes, which may lead to disuse osteoporosis in astronauts.

Speed and accuracy improvements in standard algorithm for prismatic gravitational field

2020 ◽  
Vol 222 (3) ◽  
pp. 1898-1908
Author(s):  
Toshio Fukushima
Keyword(s):  
Gravitational Field ◽  
Exact Formula ◽  
New Method ◽  
Gravity Gradient ◽  
Gradient Tensor ◽  
Gravity Gradient Tensor ◽  
Triple Difference ◽  
Transcendental Functions ◽  
Arctangent Function ◽  
Speed And Accuracy

SUMMARY By utilizing the addition theorems of the arctangent function and the logarithm, we developed a new expression of Bessel’s exact formula to compute the prismatic gravitational field using the triple difference of certain analytic functions. The use of the new expression is fast since the number of transcendental functions required is significantly reduced. The numerical experiments show that, in computing the gravitational potential, the gravity vector, and the gravity gradient tensor of a uniform rectangular parallelepiped, the new method runs 2.3, 2.3 and 3.7 times faster than Bessel’s method, respectively. Also, the new method achieves a slight increase in the computing precision. Therefore, the new method can be used in place of Bessel’s method in any situation. The same approach is applicable to the geomagnetic field computation.

scholarly journals Co-Seismic and Post-Seismic Temporal and Spatial Gravity Changes of the 2010 Mw 8.8 Maule Chile Earthquake Observed by GRACE and GRACE Follow-on

2020 ◽  
Vol 12 (17) ◽  
pp. 2768
Author(s):  
Wei Qu ◽  
Yaxi Han ◽  
Zhong Lu ◽  
Dongdong An ◽  
Qin Zhang ◽  
...  
Keyword(s):  
Gravitational Field ◽  
Hanging Wall ◽  
Suppressive Effect ◽  
Gravity Gradient ◽  
Dislocation Model ◽  
Seismogenic Fault ◽  
First Order ◽  
Gravity Changes ◽  
Maule Earthquake ◽  
Temporal And Spatial

The Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on (GRACE-FO) satellites are important for studying regional gravitational field changes caused by strong earthquakes. In this study, we chose Chile, one of Earth’s most active seismic zones to explore the co-seismic and post-seismic gravitational field changes of the 2010 Mw 8.8 Maule earthquake based on longer-term GRACE and the newest GRACE-FO data. We calculated the first-order co-seismic gravity gradient changes (GGCs) and probed the geodynamic characteristics of the earthquake. The earthquake caused significant positive gravity change on the footwall and negative gravity changes on the hanging wall of the seismogenic fault. The time series of gravity changes at typical points all clearly revealed an abrupt change caused by the earthquake. The first-order northern co-seismic GGCs had a strong suppressive effect on the north-south strip error. GRACE-FO results showed that the latest post-seismic gravity changes had obvious inherited development characteristics, and that the west coast of Chile maybe still affected by the post-seismic effect. The cumulative gravity changes simulated based on viscoelastic dislocation model is approximately consistent with the longer-term GRACE and the newest GRACE-FO observations. Our results provide important reference for understanding temporal and spatial gravity variations associated with the co-seismic and post-seismic processes of the 2010 Maule earthquake.

scholarly journals The Role of Non-tidal Atmospheric Loading in the Task of Gravity Field Estimation by Inter-Satellite Measurements

2021 ◽  
Author(s):  
I. O. Skakun ◽  
V. V. Mitrikas ◽  
V. V. Ianishevskii
Keyword(s):  
Gravitational Field ◽  
Gravity Field ◽  
Satellite Measurements ◽  
Atmospheric Loading ◽  
Field Estimation ◽  
Tidal Variations ◽  
Grace Mission ◽  
Monthly Variations ◽  
Water Height

AbstractThe paper reviews models of tidal and non-tidal variations of the Earth's gravitational field. Proposing an algorithm for the estimation of the Stokes coefficients based on inter-satellite measurements of low-orbit spacecrafts. By processing measurements of the GRACE mission, we obtained experimental estimates of gravity field monthly variations. The analysis of these values was carried out by calculating the change in the equivalent water height for a given area.

Taylor series expansion of prismatic gravitational field

2019 ◽  
Vol 220 (1) ◽  
pp. 610-660 ◽  
Author(s):  
Toshio Fukushima
Keyword(s):  
Gravitational Field ◽  
Series Expansion ◽  
Taylor Series ◽  
Taylor Series Expansion ◽  
Rectangular Prism ◽  
Gravity Gradient ◽  
Adaptive Procedure ◽  
Eighth Order ◽  
Evaluation Point ◽  
Transcendental Functions

SUMMARY The exact analytical formulae to compute the gravitational field of a rectangular prism suffer from round-off errors when the evaluation point is outside the Brillouin sphere of the prism. The error magnitude grows cubically with respect to the distance from the prism. This phenomenon is eminent in not only the gravitational potential but also the gravity vector and the gravity gradient tensor. Unfortunately, the issue of error increase is not settled efficiently by the rewriting of the formulae using the addition theorems of the transcendental functions. Besides, the computational labour of the formulae is not small since at least 18 transcendental functions are employed for the potential computation each time. In order to solve these problems, we developed up to the 16th order 3-D Taylor series expansion of all the gravitational field quantities for a uniform rectangular prism of arbitrary dimensions. For instance, the eighth order truncation guarantees the eight digit accuracy of the potential computation of a nearly cubic prism at the cost of 11 per cent of that of the fast computation of the exact formula when the distance is more than 2.7 times longer than the Brillouin sphere radius. By using a simple algorithm, we present an adaptive procedure combining the truncated series of various orders and the exact formulae in order to compute precisely and quickly the gravitational field of an assembly of prisms everywhere. Exactly the same approach is applicable to the geomagnetic field computation.

scholarly journals MODELING AND SIMULATION OF PROLATE DUAL-SPIN SATELLITE DYNAMICS IN AN INCLINED ELLIPTICAL ORBIT : CASE STUDY OF PALAPA B2R SATELLITE

2010 ◽  
Vol 3 (2) ◽  
Author(s):  
J.Muliadi ◽  
Said D.Jenie ◽  
A Budiyono
Keyword(s):  
Control System ◽  
Gravitational Field ◽  
Satellite Orbit ◽  
Equation Of Motion ◽  
Elliptical Orbit ◽  
Gravity Gradient ◽  
Satellite Dynamics ◽  
Satellite Attitude ◽  
The Stability

In response to the interest to re-use PAlapa B2R satellite nearing its End of Life (EOL) time, an idea to incline the satellite orbit in order to cover a new region has emerged in the recent years. As a prolate dual-spin vehicle, Palapa B2R has to be stabilized against its internal energy dissipation effect. This work is focused on analyzing the dynamics of the reusable satellite in its inclined orbit. The study discusses in particular the stability of the prolate dual-spin satellite in the effect of pertubed field of gravity due to the inclination of its elliptical orbit. Palapa B2R physical data was substituted into the dual-spin's equation of motion. The coefficient of zonal harmonics J2 was induced into the gravity-gradient moment term that affects the satellite attitude. The satellites's motion and attitude were then simulated in the pertubed gravitational field by J2 with the variation of orbit's eccentricity and inclination. The analysis of the satellite dynamics and its stability was conducted for designing control system for the vehicle in its new inclined orbit.

A one-dimensional self-gravitating stellar gas

1966 ◽  
Vol 25 ◽  
pp. 46-48 ◽  
Author(s):  
M. Lecar
Keyword(s):  
Gravitational Field ◽  
Phase Space ◽  
Motion Picture ◽  
Space Distribution ◽  
Two Dimensional ◽  
One Dimensional ◽  
Phase Space Distribution ◽  
Dimensional Phase Space ◽  
The Mean

“Dynamical mixing”, i.e. relaxation of a stellar phase space distribution through interaction with the mean gravitational field, is numerically investigated for a one-dimensional self-gravitating stellar gas. Qualitative results are presented in the form of a motion picture of the flow of phase points (representing homogeneous slabs of stars) in two-dimensional phase space.

Evolution of collisional systems

1984 ◽  
Vol 75 ◽  
pp. 361-362
Author(s):  
André Brahic
Keyword(s):  
Gravitational Field ◽  
Dynamical Evolution ◽  
Oblate Planet

AbstractThe dynamical evolution of planetary discs in the gravitational field of an oblate planet and a satellite is numerically simulated.

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