Computation of calibration gradients and methods for in-orbit validation of gradiometric GOCE data

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Original languageEnglish
Pages (from-to)111-118
Number of pages8
JournalEuropean Space Agency, (Special Publication) ESA SP
Issue number569
Publication statusPublished - 1 Dec 2004
EventSecond International GOCE User Workshop: GOCE, The Geoid and Oceanography - Frascati, Italy
Duration: 8 Mar 200410 Mar 2004

Abstract

The accuracy planned for GOCE gravity gradiometry requires special independent concepts for calibration and validation of the measured gravitational gradients. Although the gradiometer will be calibrated internally on ground (pre-flight) and prior to the measurement phase itself in orbit (in-flight), further external calibration, e.g., by the use of terrestrial gravity data, is obligatory to establish the relationship of the measurements to the Earth's gravitational field at the required accuracy level. To meet the accuracy of the satellite data, a region with well known gravity field parameters has to be selected for calibration. The Institut für Erdmessung at the University of Hanover has collected a data set of 5′ by 5′ gridded gravity anomalies in Central Europe. From these terrestrial gravity anomalies, gravitational gradients at GOCE altitude are computed as reference for calibration and validation purposes. The upward continuation of the gravity anomalies to the calibration gradients is carried out by two methods, namely least-squares collocation and integral formulas. Results of both methods are compared and analysed. Even without the availability of independent data, some conclusions on the quality and consistency of the observed GOCE data can be drawn by comparing measurements in the same satellite position, i.e. in satellite track cross-overs. Unfortunately, due to the orbit characteristics of the mission, one has to take into account satellite ground track cross-overs instead of identical repeat positions. Therefore, a reduction concept has to be applied to consider the differences caused by different satellite altitudes and orientations. It is shown here, that present global gravity field models meet the accuracy and resolution requirements of the reduction concept.

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Computation of calibration gradients and methods for in-orbit validation of gradiometric GOCE data. / Müller, J.; Denker, H.; Jarecki, F. et al.
In: European Space Agency, (Special Publication) ESA SP, No. 569, 01.12.2004, p. 111-118.

Research output: Contribution to journalConference articleResearchpeer review

Müller, J, Denker, H, Jarecki, F & Wolf, KI 2004, 'Computation of calibration gradients and methods for in-orbit validation of gradiometric GOCE data', European Space Agency, (Special Publication) ESA SP, no. 569, pp. 111-118.
Müller, J., Denker, H., Jarecki, F., & Wolf, K. I. (2004). Computation of calibration gradients and methods for in-orbit validation of gradiometric GOCE data. European Space Agency, (Special Publication) ESA SP, (569), 111-118.
Müller J, Denker H, Jarecki F, Wolf KI. Computation of calibration gradients and methods for in-orbit validation of gradiometric GOCE data. European Space Agency, (Special Publication) ESA SP. 2004 Dec 1;(569):111-118.
Müller, J. ; Denker, H. ; Jarecki, F. et al. / Computation of calibration gradients and methods for in-orbit validation of gradiometric GOCE data. In: European Space Agency, (Special Publication) ESA SP. 2004 ; No. 569. pp. 111-118.
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abstract = "The accuracy planned for GOCE gravity gradiometry requires special independent concepts for calibration and validation of the measured gravitational gradients. Although the gradiometer will be calibrated internally on ground (pre-flight) and prior to the measurement phase itself in orbit (in-flight), further external calibration, e.g., by the use of terrestrial gravity data, is obligatory to establish the relationship of the measurements to the Earth's gravitational field at the required accuracy level. To meet the accuracy of the satellite data, a region with well known gravity field parameters has to be selected for calibration. The Institut f{\"u}r Erdmessung at the University of Hanover has collected a data set of 5′ by 5′ gridded gravity anomalies in Central Europe. From these terrestrial gravity anomalies, gravitational gradients at GOCE altitude are computed as reference for calibration and validation purposes. The upward continuation of the gravity anomalies to the calibration gradients is carried out by two methods, namely least-squares collocation and integral formulas. Results of both methods are compared and analysed. Even without the availability of independent data, some conclusions on the quality and consistency of the observed GOCE data can be drawn by comparing measurements in the same satellite position, i.e. in satellite track cross-overs. Unfortunately, due to the orbit characteristics of the mission, one has to take into account satellite ground track cross-overs instead of identical repeat positions. Therefore, a reduction concept has to be applied to consider the differences caused by different satellite altitudes and orientations. It is shown here, that present global gravity field models meet the accuracy and resolution requirements of the reduction concept.",
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