GOCE orbit analysis: Long-wavelength gravity field determination using the acceleration approach

2012 ◽  
Vol 50 (3) ◽  
pp. 385-396 ◽  
Author(s):  
O. Baur ◽  
T. Reubelt ◽  
M. Weigelt ◽  
M. Roth ◽  
N. Sneeuw
Keyword(s):  
Gravity Field ◽  
Long Wavelength ◽  
Gravity Field Determination ◽  
Orbit Analysis

Gravity-field determination from laser observations

1977 ◽  
Vol 284 (1326) ◽  
pp. 515-527 ◽  
Keyword(s):  
Gravity Field ◽  
Spherical Harmonics ◽  
Field Model ◽  
Satellite Tracking ◽  
Sea Surface ◽  
Tracking Data ◽  
Gravity Field Model ◽  
Long Wavelength ◽  
Gravity Field Determination

Knowledge of long-wavelength features of the geopotential is significantly improved by the use of precision satellite tracking with lasers. Tracking data on nine satellites are combined with terrestrial gravimetry to obtain a spherical-harmonics representation of the geopotential complete through degree and order 24. An improved gravity-field model provides better satellite ephemerides and a reference for analysing satellite-to-sea-surface altimetry.

Combining the deep Earth and lithospheric gravity field to study the density structure of the upper mantle

2021 ◽  
Author(s):  
Bart Root ◽  
Javier Fullea ◽  
Jörg Ebbing ◽  
Zdenek Martinec
Keyword(s):  
Gravity Field ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Field Data ◽  
Wavelength Region ◽  
Density Structure ◽  
Long Wavelength ◽  
Global Gravity ◽  
Deep Earth

<p>Global gravity field data obtained by dedicated satellite missions is used to study the density distribution of the lithosphere. Different multi-data joint inversions are using this dataset together with other geophysical data to determine the physical characteristics of the lithosphere. The gravitational signal from the deep Earth is usually removed by high-pass filtering of the model and data, or by appropriately selecting insensitive gravity components in the inversion. However, this will remove any long-wavelength signal inherent to lithosphere. A clear choice on the best-suited approach to remove the sub-lithospheric gravity signal is missing. </p><p>Another alternative is to forward model the gravitational signal of these deep situated mass anomalies and subtract it from the observed data, before the inversion. Global tomography provides shear-wave velocity distribution of the mantle, which can be transformed into density anomalies. There are difficulties in constructing a density model from this data. Tomography relies on regularisation which smoothens the image of the mantle anomalies. Also, the shear-wave anomalies need to be converted to density anomalies, with uncertain conversion factors related to temperature and composition. Understanding the sensitivity of these effects could help determining the interaction of the deep Earth and the lithosphere.</p><p>In our study the density anomalies of the mantle, as well as the effect of CMB undulations, are forward modelled into their gravitational potential field, such that they can be subtracted from gravity observations. The reduction in magnitude of the density anomalies due to the regularisation of the global tomography models is taken into account. The long-wavelength region of the density estimates is less affected by the regularisation and can be used to fix the mean conversion factor to transform shear wave velocity to density. We present different modelling approaches to add the remaining dynamic topography effect in lithosphere models. This results in new solutions of the density structure of the lithosphere that both explain seismic observations and gravimetric measurements. The introduction of these dynamic forces is a step forward in understanding how to properly use global gravity field data in joint inversions of lithosphere models.</p>

scholarly journals Role of geo-potential models in gravity field determination

2009 ◽  
pp. 34-37
Author(s):  
Niraj Manandhar ◽  
Rene Forsberg
Keyword(s):  
Gravity Field ◽  
Geopotential Model ◽  
Potential Models ◽  
Geopotential Models ◽  
Gravity Field Determination ◽  
Major Emphasis

This paper sets out to describe the developments of geopotential models and its role in gravity field determination. The paper also focuses in different geopotential models those are available and in use from 1980 onwards till at present with major emphasis placed on WGS84 EGM96 geopotential model.

scholarly journals Vertical Deflections and Gravity Disturbances Derived from HY-2A Data

2020 ◽  
Vol 12 (14) ◽  
pp. 2287
Author(s):  
Xiaoyun Wan ◽  
Richard Fiifi Annan ◽  
Shuanggen Jin ◽  
Xiaoqi Gong
Keyword(s):  
Gravity Field ◽  
Systematic Errors ◽  
Mean Value ◽  
Gravity Disturbance ◽  
Long Wavelength ◽  
The North ◽  
Marine Gravity ◽  
Gravity Disturbances ◽  
Sea Surface Heights ◽  
East Component

The first Chinese altimetry satellite, Haiyang-2A (HY-2A), which was launched in 2011, has provided a large amount of sea surface heights which can be used to derive marine gravity field. This paper derived the vertical deflections and gravity disturbances using HY-2A observations for the major area of the whole Earth’s ocean from 60°S and 60°N. The results showed that the standard deviations (STD) of vertical deflections differences were 1.1 s and 3.5 s for the north component and the east component between HY-2A’s observations and those from EGM2008 and EIGEN-6C4, respectively. This indicates the accuracy of the east component was poorer than that of the north component. In order to clearly demonstrate contribution of HY-2A’s observations to gravity disturbances, reference models and the commonly used remove-restore method were not adopted in this study. Therefore, the results can be seen as ‘pure’ signals from HY-2A. Assuming the values from EGM2008 were the true values, the accuracy of the gravity disturbances was about −1.1 mGal in terms of mean value of the errors and 8.0 mGal in terms of the STD. This shows systematic errors if only HY-2A observations were used. An index of STD showed that the accuracy of HY-2A was close to the theoretical accuracy according to the vertical deflection products. To verify whether the systematic errors of gravity field were from the long wavelengths, the long-wavelength parts of HY-2A’s gravity disturbance with wavelengths larger than 500 km were replaced by those from EGM2008. By comparing with ‘pure’ HY-2A version of gravity disturbance, the accuracy of the new version products was improved largely. The systematic errors no longer existed and the error STD was reduced to 6.1 mGal.

scholarly journals GOCE: assessment of GPS-only gravity field determination

2014 ◽  
Vol 89 (1) ◽  
pp. 33-48 ◽  
Author(s):  
Adrian Jäggi ◽  
H. Bock ◽  
U. Meyer ◽  
G. Beutler ◽  
J. van den IJssel
Keyword(s):  
Gravity Field ◽  
Gravity Field Determination

What can be expected from GNSS tracking of satellite constellations for temporal gravity field model determination?

2020 ◽  
Vol 222 (1) ◽  
pp. 661-677
Author(s):  
Hao Zhou ◽  
Zebing Zhou ◽  
Zhicai Luo ◽  
Kang Wang ◽  
Min Wei
Keyword(s):  
Gravity Field ◽  
Field Model ◽  
Geoid Height ◽  
Error Component ◽  
Expected Improvement ◽  
Gps Tracking ◽  
Satellite Constellations ◽  
Gravity Field Model ◽  
Gravity Field Determination ◽  
Temporal Gravity

SUMMARY The goal of this contribution is to investigate the expected improvement of temporal gravity field determination via a couple of high-low satellite-to-satellite tracking (HLSST) missions. The simulation system is firstly validated by determining monthly gravity field models within situ GRACE GPS tracking data. The general consistency between the retrieved solutions and those developed by other official agencies indicates the good performance of our software. A 5-yr full-scale simulation is then performed using the full error sources including all error components. Analysis of each error component indicates that orbit error is the main contributor to the overall HLSST-derived gravity field model error. The noise level of monthly solution is therefore expected to reduce 90 per cent in terms of RMSE over ocean when the orbit accuracy improves for a magnitude of one order. As for the current HLSST mission consisting of a current GNSS receiver and an accelerometer (10−10 and 10−9 m s–2 noise for sensitive and non-sensitive axes), it is expected to observe monthly (or weekly) gravity solution at the spatial resolution of about 1300 km (or 2000 km). As for satellite constellations, a significant improvement is expected by adding the second satellite with the inclination of 70° and the third satellite with the inclination of 50°. The noise reduction in terms of cumulative geoid height error is approximately 51 per cent (or 62 per cent) when the observations of two (or three) HLSST missions are used. Moreover, the accuracy of weekly solution is expected to improve 40–70 per cent (or 27–59 per cent) for three (or two) HLSST missions when compared to one HLSST mission. Due to the low financial costs, it is worthy to build a satellite constellation of HLSST missions to fill the possible gaps between the dedicated temporal gravity field detecting missions.

scholarly journals SLR, GRACE and Swarm Gravity Field Determination and Combination

2019 ◽  
Vol 11 (8) ◽  
pp. 956 ◽  
Author(s):  
Ulrich Meyer ◽  
Krzysztof Sosnica ◽  
Daniel Arnold ◽  
Christoph Dahle ◽  
Daniela Thaller ◽  
...  
Keyword(s):  
Mass Transport ◽  
Gravity Field ◽  
Large Scale ◽  
Mass Gain ◽  
Normal Equation ◽  
Polar Regions ◽  
Swarm Satellites ◽  
Gravity Fields ◽  
Long Time ◽  
Gravity Field Determination

Satellite gravimetry allows for determining large scale mass transport in the system Earth and to quantify ice mass change in polar regions. We provide, evaluate and compare a long time-series of monthly gravity field solutions derived either by satellite laser ranging (SLR) to geodetic satellites, by GPS and K-band observations of the GRACE mission, or by GPS observations of the three Swarm satellites. While GRACE provides gravity signal at the highest spatial resolution, SLR sheds light on mass transport in polar regions at larger scales also in the pre- and post-GRACE era. To bridge the gap between GRACE and GRACE Follow-On, we also derive monthly gravity fields using Swarm data and perform a combination with SLR. To correctly take all correlations into account, this combination is performed on the normal equation level. Validating the Swarm/SLR combination against GRACE during the overlapping period January 2015 to June 2016, the best fit is achieved when down-weighting Swarm compared to the weights determined by variance component estimation. While between 2014 and 2017 SLR alone slightly overestimates mass loss in Greenland compared to GRACE, the combined gravity fields match significantly better in the overlapping time period and the RMS of the differences is reduced by almost 100 Gt. After 2017, both SLR and Swarm indicate moderate mass gain in Greenland.

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.

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