Calibration of satellite gradiometer data aided by ground gravity data

Arabelos, D.; Tscherning, C. C.

doi:10.1007/s001900050201

Cited by 28 publications

(18 citation statements)

References 4 publications

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“…Conversely, it may be possible to check the CM observations from a combination of existing gravity field information and the SST data. Earlier results can be found in Arabelos and Tscherning (1998) and Koop et al (2002).…”

Section: Introductionmentioning

confidence: 64%

“…The external calibration of the GOCE gradiometer measurements using terrestrial data has been studied by Arabelos and Tscherning (1998) using real data for an area in Western Canada, but east of the Rocky Mountains, where the gravity field is very smooth. Using LSC, gravity gradient data were generated at satellite altitude along simple north-going or east-going tracks.…”

Section: Calibration Of Gravity Gradients With Errorsmentioning

confidence: 99%

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Calibration of GOCE SGG data using high?low SST, terrestrial gravity data and global gravity field models

Bouman

Koop

Tscherning³

et al. 2004

Journal of Geodesy

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Abstract. It is the aim of the GOCE mission to determine a model of the Earth's gravity field with high accuracy and resolution. For this purpose, gravity gradients will be measured in combination with highlow satellite-to-satellite tracking. The gravity gradients are derived from pair-wise differenced accelerations as determined by the six three-axes accelerometers that form the GOCE gradiometer. Since the measured accelerations suffer from errors of a random and systematic nature, the gravity gradients may suffer from random and systematic errors as well. Systematic errors are, for example, a scale factor and a bias. The common accelerations of the paired accelerometers also are contaminated with such errors. The common accelerations are used in the drag-free control of the satellite and are important for the separation of the gravitational and non-gravitational forces in the gravity field determination. The checking of the gravity gradients and the common accelerations against independent data (i.e. external to the GOCE satellite) in order to free the observations as well as is possible from systematic errors is called external calibration. The possibilities and limitations of using terrestrial gravity data and global gravity models for external calibration of the gravity gradients are reviewed. It turns out that the determination of a gravity gradient scale factor and bias using just the accurate knowledge of the central term and the flattening (J 2 ) of the Earth's gravity field is not good enough. When global gravity field models are used for the calibration, higher degrees and orders should be taken into account as well. With today's existing global models it seems to be possible to remove the greater part of the systematic errors of the GOCE gradients. A gravity gradient bias can accurately be recovered using terrestrial gravity data in a regional approach with least squares collocation. However, since regional data are used it may not be possible to determine calibration parameters valid for the whole (global) gravity gradient data set. Nevertheless, regional terrestrial gravity data could be used to validate the measured and calibrated gravity gradients. In addition, a possible use of GOCE high-low satellite-to-satellite tracking data to calibrate the common accelerations is explored; it is shown that this approach fails. If more accurate gravity field information becomes available then such a calibration may become feasible.

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Section: Introductionmentioning

confidence: 64%

Section: Calibration Of Gravity Gradients With Errorsmentioning

confidence: 99%

Calibration of GOCE SGG data using high?low SST, terrestrial gravity data and global gravity field models

Bouman

Koop

Tscherning³

et al. 2004

Journal of Geodesy

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“…The calibration is based on the gravity data from four regions selected because of available high-quality gravity data and smoothly varying gravity anomalies (Arabelos and Tscherning 1998). The four areas are located in Northern Europe, Canada and Australia, and their geographical distribution is shown in Fig.…”

Section: Terrestrial Gravity Datamentioning

confidence: 99%

“…This allows flybys of 200 s duration in each area, which corresponds to the lower part of the MB of 5 mHz. The calibration method was originally intended to determine GG bias, tilt and SF using LSC (least squares collocation), see (Arabelos and Tscherning 1998;, which requires the use of a band wise unrestricted GGs and for data distributed over a period of, e.g. 14 days, which would include crossover quality checks and implicit utilization of the Laplace equation.…”

Section: Terrestrial Gravity Datamentioning

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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“…Therefore, in order to possibly correct for remaining errors after internal calibration, a third calibration step is required, which is called external calibration (or absolute calibration). It is performed during or after the mission and typically makes use of external gravity data (Arabelos and Tscherning, 1998;Koop et al, 2002).…”

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confidence: 99%

Error assessment of GOCE SGG data using along track interpolation

Bouman

Koop

2003

Adv. Geosci.

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Abstract. GOCE will be the first satellite gravity mission measuring gravity gradients in space using a dedicated instrument called a gradiometer. High resolution gravity field recovery will be possible from these gradients. Such a recovery requires a proper description of the gravity gradient errors, where the a priori error model is for example based on end-to-end instrument simulations. One way to test the error model against real data, i.e. to see if the a priori model really describes the actual error, is to compare along track interpolated gradients with the measured gradients. The difference between the interpolated and measured gravity gradients is caused by, among others, the interpolation error and the measurement errors. The idea is that if the interpolation error is small enough, then the differences should be predicted reasonably well by the error model. This paper discusses a simulation study where the gravity gradient errors are generated with an end-to-end instrument simulator. The measurement error will be compared with the interpolation error and we will assess the latter as a function of the sampling interval.

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Calibration of satellite gradiometer data aided by ground gravity data

Cited by 28 publications

References 4 publications

Calibration of GOCE SGG data using high?low SST, terrestrial gravity data and global gravity field models

Calibration of GOCE SGG data using high?low SST, terrestrial gravity data and global gravity field models

GOCE gravitational gradients along the orbit

Error assessment of GOCE SGG data using along track interpolation

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