Monday, July 12, 2010
The Gravity Recovery and Climate Experiment (GRACE) mission is included in a recent article on the Environment 360 Web site as one of the crucial ways scientists are keeping track of changes in the Earth’s climate from space.
GRACE is a twin-satellite array that measures changes in gravity around the world. Scores of scientists have used data collected by the satellites to track changes ranging from Greenland’s and Antarctica’s ice sheets to the amount of water in California’s aquifers.
Engineering Professor Byron Tapley of The University of Texas at Austin is the principal investigator on the GRACE project.
The E360 article described how GRACE operates:
“The way it works is ingenious: GRACE is actually two identical satellites, orbiting in formation 220 kilometers (137 miles) apart. When they approach an area of excess mass — a mountain range, for example — the extra gravity tugs on the lead satellite, making it speed up a little and increasing the distance between the two. When the satellites approach a mass deficit, such as a crater, the leading satellite slows. By measuring the distance between the two orbiters constantly and precisely, scientists can calculate the Earth’s surprisingly lumpy gravity field with exquisite accuracy.”
The article also talks about other Earth-observing satellites: ICESat (which stopped working in October), Ocean Circulation Explorer and CryoSat-2.
In the other GRACE news, its mission has been extended through the end of its orbit life, which is expected in 2015. NASA and its German counterpart agency, the German Aerospace Center (DLR), signed an extension agreement in June.
GRACE has been in orbit for more than eight years.
NASA and DLR developed the Grace mission. NASA provided the instruments and selected satellite components, plus data validation and archiving. DLR provided the primary satellite components, launch services and operations.