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Integrated Program / Observational Stratgies/ Strategy 4: Variability of Earth's Gravity Field  






Gravity AnomalySatellite gravity measurements have demonstrated the clear importance of determining the spatial and temporal variability of the Earth's global gravity field. There are now three dedicated high-resolution gravity missions- GRACE, CHAMP, and the European Space Agency's Gravity Field and Steady State Ocean Circulation Explorer (GOCE) - either in orbit or planned. Each mission makes use of a different technique for gravity measurement. The 1997 National Research Council report “Satellite Gravity and the Geosphere” outlined in detail the compelling rationale for temporal measurements of the gravity field to the cryospheric, hydrological, atmospheric, oceanographic, and solid-Earth sciences.

Gravity missions such as GRACE, when combined with high-resolution radar altimetry missions such as Jason, will allow for the identification of the steric component of sea-level variations and the partitioning of water storage among continents, oceans, and ice sheets and glaciers. Combined use of timevariable gravity data and ice-mass data (e.g., from ICESat) can help quantify the mantle response to past and present glaciation. Because Earth-rotation parameters and gravity anomaly measurements are both manifestations of mass redistribution, geodetic and gravity measurements are excellent examples of synergy, allowing a better understanding of global mass transport in the Earth system.

Suggested mission phasing and requirements

Immediate (1–5 years): Monthly estimation to within 10 millimeters of surface waterequivalent
load at a few hundred kilometers spatial resolution using existing satellites such as GRACE.

Near Term (5–10 years): GRACE follow-on mission demonstrating satellite-to-satellite laser interferometry technology.

Long term (10–25 years): Gravity measurement improved by 2–3 orders of magnitude
in sensitivity using satellite-to-satellite laser interferometry or spaceborne quantum gradiometer


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