Abstract
The Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite aimed at determining the Earth’s mean gravity field. GOCE delivered gravity gradients containing directional information, which are complicated to use because of their error characteristics and because they are given in a rotating instrument frame indirectly related to the Earth. We compute gravity gradients in grids at 225 km and 255 km altitude above the reference ellipsoid corresponding to the GOCE nominal and lower orbit phases respectively, and find that the grids may contain additional high-frequency content compared with GOCE-based global models. We discuss the gradient sensitivity for crustal depth slices using a 3D lithospheric model of the North-East Atlantic region, which shows that the depth sensitivity differs from gradient to gradient. In addition, the relative signal power for the individual gradient component changes comparing the 225 km and 255 km grids, implying that using all components at different heights reduces parameter uncertainties in geophysical modelling. Furthermore, since gravity gradients contain complementary information to gravity, we foresee the use of the grids in a wide range of applications from lithospheric modelling to studies on dynamic topography, and glacial isostatic adjustment, to bedrock geometry determination under ice sheets.
Highlights
The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) was the European Space Agency’s (ESA) first satellite gravity mission that delivered scientific data from November 2009 until October 2013
Gradients in the Local North-Oriented Frame (LNOF) are given[10,11,12]. These gradients are rotated to the LNOF after replacement of the long wavelength signal below the Measurement Bandwidth (MBW) with gradients from a global gravity field model, where VXY and VYZ are computed from such a model[12]
Global gravity gradient grids at 225 km above the Earth’s surface are shown in Fig. 1, where the gradients in the LNOF are in the North, West, Up (N, W, U) frame, which is the convention adopted for GOCE12
Summary
The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) was the European Space Agency’s (ESA) first satellite gravity mission that delivered scientific data from November 2009 until October 2013. Our global gravity gradient grids have a constant height above the oblate reference ellipsoid calculated in two heights: 255 and 225 km, which correspond to the GOCE nominal and lower orbit phase, respectively Their advantage over global models in terms of Stokes coefficients is that the gravity gradients are readily available for geophysical modelling and may contain more detailed signal. Their advantage over GRF and LNOF gradients or spherical grids[18] is that they are at relatively constant height with respect to the Earth’s topography because they are given on homothetic ellipsoids (i.e. with WGS84 eccentricity but different semi-major axis).
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