The Science Behind the GRACE Mission
Gravity is the invisible force that pulls two masses together. The branch of science dealing with obtaining precise measurements of the Earth, mapping points on the surface, and studying its gravitational field is known as geodesy. Producing such a precise model of the changes in gravity over the Earth's surface has proven to be a formidable task.
Currently, data from several dozen satellites must be combined to produce a model of Earth's gravitational field. These models do a good job at simulating the large-scale features of Earth's gravitational field but cannot resolve finer-scale features. Adding data from ground-based measurements and airborne altimeters allows for more precise measurement over large bodies of water. The unique design of the GRACE mission (twin-satellites flying in formation) is expected to lead to an improvement of several orders of magnitude in these gravity measurements and allow much improved resolution of the broad to finer-scale features of Earth's gravitational field over both land and sea.
A secondary experiment that GRACE will perform is to examine how the atmosphere affects signals from the Global Positioning System (GPS).
The GRACE mission combined with other existing sources of data will greatly improve our understanding of:
GRACE Gravity Model 02 - Publicly released October 29, 2004
GRACE Gravity Model 01 - Released July 2003