HEPL Seminar The GRACE Mission

The GRACE Mission: Status and Science Results

The GRACE (Gravity Recovery and Climate Experiment) mission will accurately map variations in the Earth's gravity field over its 5-year lifetime using two identical spacecraft flying about 220 kilometers apart in a polar orbit 500 kilometers above the Earth. The gravity field is mapped by making accurate measurements of the distance between the two satellites, using GPS and a microwave ranging system. Launched in March 2002, the two GRACE satellites have collected over two years of data. The gravity models developed with this data are more than an order of magnitude better at the long and mid wavelengths than previous models. The error estimates indicate a 1-cm accuracy uniformly over the land and ocean regions, a consequence of the highly accurate, global and homogenous nature of the GRACE data. Initial results from the GRACE mission also show seasonal variability of the Earth's gravity field at monthly intervals with a 400 km resolution, and a global geoid accuracy of 2-3 mm. These early results are a strong affirmation of the GRACE mission concept.