Due to an uneven distribution of mass inside the Earth, the Earth's gravity field is not uniform - that is, it has "lumps". By far the largest is a flattening at the poles, called the Earth's oblateness, but in this model we've greatly exaggerated the scale so that many smaller features can be seen. The GRACE Mission will map out the precise location and size of these lumps, enabling greater understanding of the structure of the Earth. Additionally, GRACE will monitor the mass and location of water as it moves around on the surface of the Earth, cycling between the land, oceans, and polar ice caps. Credit: The University of Texas, NASA Jet Propulsion Laboratory, and the GeoForschungsZentrum Potsdam
The primary goal of the GRACE mission is to accurately map variations in the Earth's gravity field over its 5-year lifetime. The GRACE mission has two identical spacecrafts flying about 220 kilometers apart in a polar orbit 500 kilometers above the Earth.
It maps the Earth's gravity fields by making accurate measurements of the distance between the two satellites, using geodetic quality Global Positioning System (GPS) receivers and a microwave ranging system. This provides scientists from all over the world with an efficient and cost-effective way to map the Earth's gravity fields with unprecedented accuracy. The results from this mission yield crucial information about the distribution and flow of mass within the Earth and its surroundings.
The gravity variations that GRACE studies include: changes due to surface and deep currents in the ocean; runoff and ground water storage on land masses; exchanges between ice sheets or glaciers and the oceans; and variations of mass within the Earth. Another goal of the mission is to create a better profile of the Earth's atmosphere. The results from GRACE make a huge contribution to NASA's Earth science goals, Earth Observation System (EOS) and global climate change studies.
GRACE is a joint partnership between the NASA in the United States and Deutsche Forschungsanstalt fur Luft und Raumfahrt (DLR) in Germany. Project management and systems engineering activities are carried out by the Jet Propulsion Laboratory.
Principal Investigator: Dr. Byron Tapley
University of Texas Center for Space Research (UTCSR), Austin, TX
Co-Principal Investigator: Dr. Frank Flechtner
GeoForschungsZentrum (GFZ) Potsdam, Germany