GRACE (Gravity Recovery and Climate Experiment)
Two identical spacecraft that, over a five-year period, will measure and
map variations in Earth's gravitational field, and track ocean circulation
and the movement of ocean heat to the poles. Selected as the second mission
in NASA's ESSP (Earth System Science Pathfinder)
program, the dual satellites of GRACE fly in the same orbital plane, one
220 km behind the other, at an altitude of about 550 km. However, the distance
between them changes as they are influenced differently by subtle gravitational
changes over such terrestrial landforms as ice sheets and mountain ranges.
By continuously measuring the distance between the two satellites, scientists
are able to chart Earth's gravitational field to a new degree of accuracy.
In addition, GRACE is yielding novel information about Earth's atmospheric
profile and ocean circulation. The mission is a joint partnership between
NASA and the German center for aerospace research, DLR.
||Mar. 17, 2002
||485 km × 89°
AND SPACE PROBES