|
 Satellite
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
technology.
|
|
