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| Titel |
Gravity gradient preprocessing at the GOCE HPF |
| VerfasserIn |
J. Bouman, S. Rispens, T. Gruber, E. Schrama, P. Visser, C. C. Tscherning, M. Veicherts |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025062
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| Zusammenfassung |
| One of the products derived from the GOCE observations are the gravity gradients. These
gravity gradients are provided in the Gradiometer Reference Frame (GRF) and are calibrated
in-flight using satellite shaking and star sensor data. In order to use these gravity
gradients for application in Earth sciences and gravity field analysis, additional
pre-processing needs to be done, including corrections for temporal gravity field signals to
isolate the static gravity field part, screening for outliers, calibration by comparison
with existing external gravity field information and error assessment. The temporal
gravity gradient corrections consist of tidal and non-tidal corrections. These are all
generally below the gravity gradient error level, which is predicted to show a 1/f
behaviour for low frequencies. In the outlier detection the 1/f error is compensated
for by subtracting a local median from the data, while the data error is assessed
using the median absolute deviation. The local median acts as a high-pass filter
and it is robust as is the median absolute deviation. Three different methods have
been implemented for the calibration of the gravity gradients. All three methods
use a high-pass filter to compensate for the 1/f gravity gradient error. The baseline
method uses state-of-the-art global gravity field models and the most accurate results
are obtained if star sensor misalignments are estimated along with the calibration
parameters. A second calibration method uses GOCE GPS data to estimate a low degree
gravity field model as well as gravity gradient scale factors. Both methods allow to
estimate gravity gradient scale factors down to the 10-3 level. The third calibration
method uses high accurate terrestrial gravity data in selected regions to validate
the gravity gradient scale factors, focussing on the measurement band. Gravity
gradient scale factors may be estimated down to the 10-2 level with this method. |
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