Exploring gravity field determination from orbit perturbations of the European Gravity Mission GOCE

Visser, Peter; IJssel, José van den; Koop, R.; Klees, R.

doi:10.1007/s001900000155

Cited by 35 publications

(24 citation statements)

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“…For this case, which is also shown in Visser et al (2001), geoid errors are generally negligible with a maximum of 0.4 cm and an RMS of 0.4 mm if no weight optimization takes place at all. (See Table 1, which gives maximum, RMS and average geoid errors as well as the range of the estimated variance components.…”

Section: Resultssupporting

confidence: 70%

“…Simulated noise-free data and partials files, computed from the GEODYN II orbit determination software (McCarthy et al 1993), have kindly been provided by P. Visser. A detailed description is given in Visser et al (2001), where this data set has been used in a comparative study on the quality of different recovery methods. At the time of writing, it is indeed expected that the variational approach will be followed in the derivation of the official ESA level-2 gravity field product from the GPS POD.…”

Section: Descriptionmentioning

confidence: 99%

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A Monte-Carlo technique for weight estimation in satellite geodesy

Kusche

2003

Journal of Geodesy

106

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Abstract. Precise orbit determination, and satellite-geodetic applications such as gravity field modelling or satellite altimetry, rely on different observation types and groups that have to be processed in a common parameter estimation scheme. Naturally, the choice of the relative weights for these data sets as well as for added prior information is of importance for obtaining reliable estimates of the unknown parameters and their associated covariance matrices. If the observations are predominantly affected by random errors and systematic errors play a minor role, variance component models can be applied. However, most of the methods proposed so far for variance component estimation involve repeated inversion of large matrices, resulting in intensive computations and large storage requirements if more than a few hundred unknowns are to be determined. In addition, these matrices are not necessarily provided as standard output from common geodetic least-squares estimation software. Therefore, a method is proposed which is based on Monte-Carlo estimation of the redundancy contributions of disjunctive observation groups. The method can handle unknown variance components without the need for repeated inversion of matrices. It is computationally simple, numerically stable and easy to implement. Its application is demonstrated in an experiment concerning low-medium-degree gravity field recovery from simulated orbit perturbations of the GOCE mission, and compared in performance with Lerch's method of subset solutions.

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Section: Resultssupporting

confidence: 70%

Section: Descriptionmentioning

confidence: 99%

A Monte-Carlo technique for weight estimation in satellite geodesy

Kusche

2003

Journal of Geodesy

106

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“…The observations are assumed to be provided continuously with a constant time step of 1 s. The relation between SH gravity field coefficients and observations is given by wellestablished and tested transfer functions (e.g. Schrama 1991;Sneeuw 2000;Visser 1992Visser , 2005Visser et al 1994Visser et al , 2001Visser et al , 2003. These transfer functions are used to set up the observation equations, which are to be solved by the weighted least-squares method (Sect.…”

Section: Mission Scenariosmentioning

confidence: 99%

Dependency of Resolvable Gravitational Spatial Resolution on Space-Borne Observation Techniques

Visser

Schrama

Sneeuw

et al. 2011

Geodesy for Planet Earth

Self Cite

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The so-called Colombo-Nyquist (Colombo, The global mapping of gravity with two satellites, 1984) rule in satellite geodesy has been revisited. This rule predicts that for a gravimetric satellite flying in a (near-)polar circular repeat orbit, the maximum resolvable geopotential spherical harmonic degree (l max ) is equal to half the number of orbital revolutions (n r ) the satellite completes in one repeat period. This rule has been tested for different observation types, including geoid values at sea level along the satellite ground track, orbit perturbations (radial, along-track, cross-track), low-low satellite-to-satellite tracking, and satellite gravity gradiometry observations (all three diagonal components). Results show that the Colombo-Nyquist must be reformulated. Simulations indicate that the maximum resolvable degree is in fact equal to kn r + 1, where k can be equal to 1, 2, or even 3 depending on the combination of observation types. However, the original rule is correct to some extent, considering that the quality of recovered gravity field models is homogeneous as a function of geographical longitude as long as l max < n r /2.

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“…These time series then serve as observables for the first module. Normal equations will then be formed for a combined least-squares estimation of dynamic orbit and accelerometer calibration parameters and gravity field coefficients based on the numerical integration of the variational equations (Visser et al 2001). For GOCE, use can be made of the common-mode accelerations to represent the remaining non-gravitational accelerations left by the Drag-Free Control (DFC).…”

Section: Validation Of Gradiometer Observations By Gpsmentioning

confidence: 99%

GOCE gravitational gradients along the orbit

Bouman¹,

Fiorot

Fuchs³

et al. 2011

J Geod

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GOCE is ESA's gravity field mission and the first satellite ever that measures gravitational gradients in space, that is, the second spatial derivatives of the Earth's gravitational potential. The goal is to determine the Earth's mean gravitational field with unprecedented accuracy at spatial resolutions down to 100 km. GOCE carries a gravity gradiometer that allows deriving the gravitational gradients with very high precision to achieve this goal. There are two types of GOCE Level 2 gravitational gradients (GGs) along the orbit: the gravitational gradients in the gradiometer reference frame (GRF) and the gravitational gradients in the local north oriented frame (LNOF) derived from the GGs in the GRF by point-wise rotation. Because the V X X , V Y Y , V Z Z and V X Z are much more accurate than V XY and V Y Z , and because the error of the accurate GGs increases for low frequencies, the rotation requires that part of the measured GG signal is replaced by model signal. However, the actual quality of the gradients in GRF and LNOF needs to be assessed. We analysed the outliers in the GGs, validated the GGs in the GRF using independent gravity field information and compared their assessed error with the requirements. In addition, we compared the GGs in the LNOF with state-of-the-art global gravity field models and determined the model contribution to the rotated GGs. We found that the percentage of detected outliers is below 0.1% for all GGs, and external gravity data confirm that the GG scale factors do not differ from one down to the 10 −3 level. Furthermore, we found that the error of V X X and V Y Y is approximately at the level of the requirement on the gravitational gradient trace, whereas the V Z Z error is a factor of 2-3 above the requirement for higher frequencies. We show that the model contribution in the rotated GGs is 2-35% dependent on the gravitational gradient. Finally, we found that GOCE gravitational gradients and gradients derived from EIGEN-5C and EGM2008 are consistent over the oceans, but that over the continents the consistency may be less, especially in areas with poor terrestrial gravity data. All in all, our analyses show that the quality of the GOCE gravitational gradients is good and that with this type of data valuable new gravity field information is obtained.

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Exploring gravity field determination from orbit perturbations of the European Gravity Mission GOCE

Cited by 35 publications

References 0 publications

A Monte-Carlo technique for weight estimation in satellite geodesy

A Monte-Carlo technique for weight estimation in satellite geodesy

Dependency of Resolvable Gravitational Spatial Resolution on Space-Borne Observation Techniques

GOCE gravitational gradients along the orbit

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