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| Titel |
Recovering the time-variable gravitational field using satellite gradiometry: requirements and gradiometer concept |
| VerfasserIn |
Karim Douch, Jürgen Müller, Gerhard Heinzel, Hu Wu |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150414
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| Publikation (Nr.) |
 EGU/EGU2017-14875.pdf |
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| Zusammenfassung |
| The successful GRACE mission and its far-reaching benefits have highlighted the interest to
continue and extend the mapping of the Earth’s time-variable gravitational field with
follow-on missions and ideally a higher spatiotemporal resolution.
Here, we would like to put forward satellite gravitational gradiometry as an alternative
solution to satellite-to-satellite tracking for future missions. Besides the higher sensitivity to
smaller scales compared to GRACE-like missions, a gradiometry mission would only
require one satellite and would provide a direct estimation of a functional of the
gravitational field. GOCE, the only gradiometry mission launched so far, was not
sensitive enough to map the time-variable part of the gravity field. However, the
unprecedented precision of the state-of-the-art optical metrology system on-board the
LISA PATHFINDER satellite has opened the way to more performant space inertial
sensors.
We will therefore examine whether it is technically possible to go beyond GOCE
performances and to quantify to what extent the time-variable gravitational field
could be determined. First, we derive the requirements on the knowledge of the
attitude and the position of the satellite and on the measured gradients in terms of
sensitivity and calibration accuracy for a typical repeat low-orbit. We conclude in
particular that a noise level smaller than 0.1 mE∕√Hz-- is required in the measurement
bandwidth [5x10−4 ; 10−2]Hz so as to be sensitive to the time-variable gravity signal.
We introduce then the design and characteristics of the new gradiometer concept
and give an assessment of its noise budget. Contrary to the GOCE electrostatic
gradiometer, the position of the test-mass in the accelerometer is measured here by laser
interferometry rather than by a capacitive readout system, which improves the overall
measurement chain. Finally, the first results of a performance analysis carried out thanks
to an end-to-end simulator are discussed and compared to the previously defined
requirements. |
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