TY - JOUR

T1 - Computation of calibration gradients and methods for in-orbit validation of gradiometric GOCE data

AU - Müller, J.

AU - Denker, H.

AU - Jarecki, F.

AU - Wolf, K. I.

PY - 2004/12/1

Y1 - 2004/12/1

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=22144434463&partnerID=8YFLogxK

M3 - Conference article

AN - SCOPUS:22144434463

SP - 111

EP - 118

JO - European Space Agency, (Special Publication) ESA SP

JF - European Space Agency, (Special Publication) ESA SP

SN - 0379-6566

IS - 569

T2 - Second International GOCE User Workshop: GOCE, The Geoid and Oceanography

Y2 - 8 March 2004 through 10 March 2004

ER -