Gravity-field determination from laser observations

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.

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

Geophysical Journal International ◽

10.1093/gji/ggaa177 ◽

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.

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A degree-100 lunar gravity model from the Chang’e 5T1 mission

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936802 ◽

2020 ◽

Vol 636 ◽

pp. A45

Author(s):

Jianguo Yan ◽

Shanhong Liu ◽

Chi Xiao ◽

Mao Ye ◽

Jianfeng Cao ◽

...

Keyword(s):

Gravity Field ◽

Field Model ◽

Tracking Data ◽

Lunar Gravity ◽

Love Number ◽

Orbital Inclination ◽

Gravity Field Model ◽

New Model ◽

Lunar Gravity Field ◽

Formal Error

Context. Chinese lunar missions have grown in number over the last ten years, with an increasing focus on radio science investigations. In previous work, we estimated two lunar gravity field models, CEGM01 and CEGM02. The recently lunar mission, Chang’e 5T1, which had an orbital inclination between 18 and 68 degrees, and collected orbital tracking data continually for two years, made an improved gravity field model possible. Aims. Our aim was to estimate a new lunar gravity field model up to degree and order 100, CEGM03, and a new tidal Love number based on the Chang’e 5T1 tracking data combined with the historical tracking data used in the solution of CEGM02. The new model makes use of tracking data with this particular inclination, which has not been used in previous gravity field modeling. Methods. The solution for this new model was based on our in-house software, LUGREAS. The gravity spectrum power, post-fit residuals after precision orbit determination (POD), lunar surface gravity anomalies, correlations between parameters, admittance and coherence with topography model, and accuracy of POD were analyzed to validate the new CEGM03 model. Results. We analyzed the tracking data of the Chang’e 5T1 mission and estimated the CEGM03 lunar gravity field model. We found that the two-way Doppler measurement accuracy reached 0.2 mm s−1 with 10 s integration time. The error spectrum shows that the formal error for CEGM03 was at least reduced by about 2 times below the harmonic degree of 20, when compared to the CEGM02 model. The admittance and correlation of gravity and topography was also improved when compared to the correlations for the CEGM02 model. The lunar potential Love number k2 was estimated to be 0.02430±0.0001 (ten times the formal error). Conclusions. From the model analysis and comparison of the various models, we identified improvements in the CEGM03 model after introducing Chang’e 5T1 tracking data. Moreover, this study illustrates how the low and middle inclination orbits could contribute better accuracy for a low degree of lunar gravity field.

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Applying spectral leakage corrections to gravity field determination from satellite tracking data

Geophysical Journal International ◽

10.1111/j.1365-246x.2010.04585.x ◽

2010 ◽

Cited By ~ 1

Author(s):

Sander Goossens

Keyword(s):

Gravity Field ◽

Satellite Tracking ◽

Tracking Data ◽

Spectral Leakage ◽

Gravity Field Determination

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A simulation study for anticipated accuracy of lunar gravity field model by SELENE tracking data

Advances in Space Research ◽

10.1016/j.asr.2007.03.066 ◽

2008 ◽

Vol 42 (2) ◽

pp. 331-336 ◽

Cited By ~ 21

Author(s):

Koji Matsumoto ◽

Hideo Hanada ◽

Noriyuki Namiki ◽

Takahiro Iwata ◽

Sander Goossens ◽

...

Keyword(s):

Gravity Field ◽

Simulation Study ◽

Field Model ◽

Tracking Data ◽

Lunar Gravity ◽

Gravity Field Model ◽

Lunar Gravity Field

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The earth’s gravity field recovery using the third invariant of the gravity gradient tensor from GOCE

Scientific Reports ◽

10.1038/s41598-021-81840-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Lin Cai ◽

Xiaoyun Wan ◽

Houtse Hsu ◽

Jiangjun Ran ◽

Xiangchao Meng ◽

...

Keyword(s):

Gravity Field ◽

Field Model ◽

Gravity Gradient ◽

Gravity Gradients ◽

Gravity Field Model ◽

Gravity Gradient Tensor ◽

The Third ◽

Third Invariant ◽

Gravity Field Determination ◽

2D Fft

AbstractDue to the independence of the gradiometer instrument’s orientation in space, the second invariant $$I_2$$ I 2 of gravity gradients in combination with individual gravity gradients are demonstrated to be valid for gravity field determination. In this contribution, we develop a novel gravity field model named I3GG, which is built mainly based on three novel elements: (1) proposing to utilize the third invariant $$I_3$$ I 3 of the gravity field and steady-state ocean circulation explorer (GOCE) gravity gradient tensor, instead of using the $$I_2$$ I 2 , similar to the previous studies; (2) applying an alternative two-dimensional fast fourier transform (2D FFT) method; (3) showing the advantages of $$I_3$$ I 3 over $$I_2$$ I 2 in the effect of measurement noise from the theoretical and practical computations. For the purpose of implementing the linearization of the third invariant, this study employs the theory of boundary value problems with sphere approximation at an accuracy level of $$O(J_2^2\cdot T_{ij})$$ O ( J 2 2 · T ij ) . In order to efficiently solve the boundary value problems, we proposed an alternative method of 2D FFT, which uses the coherent sampling theory to obtain the relationship between the 2D FFT and the third invariant measurements and uses the pseudo-inverse via QR factorization to transform the 2D Fourier coefficients to spherical harmonic ones. Based on the GOCE gravity gradient data of the nominal mission phase, a novel global gravity field model (I3GG) is derived up to maximum degree/order 240, corresponding to a spatial resolution of 83 km at the equator. Moreover, in order to investigate the differences of gravity field determination between $$I_3$$ I 3 with $$I_2$$ I 2 , we applied the same processing strategy on the second invariant measurements of the GOCE mission and we obtained another gravity field model (I2GG) with a maximum degree of 220, which is 20 degrees lower than that of I3GG. The root-mean-square (RMS) values of geoid differences indicates that the effects of measurement noise of I3GG is about 20% lower than that on I2GG when compared to the gravity field model EGM2008 (Earth Gravitational Model 2008) or EIGEN-5C (EIGEN: European Improved Gravity model of the Earth by New techniques). Then the accuracy of I3GG is evaluated independently by comparison the RMS differences between Global Navigation Satellite System (GNSS)/leveling data and the model-derived geoid heights. Meanwhile, the re-calibrated GOCE data released in 2018 is also dealt with and the corresponding result also shows the similar characteristics.

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