Know Your Earth 3.0: GRACE
About Byron Tapley
Byron Tapley is the Gravity Recovery and Climate Experiment (GRACE) mission principal investigator. GRACE was the first NASA Earth System Science Pathfinder Mission to achieve orbit. While the initial mission was for five years, GRACE currently has a decade of amazing science to its credit. Tapley is a member of the National Academy of Engineering, and he is a fellow member of the American Institute of Aeronautics and Astronautics, the American Geophysical Union and the American Association for the Advancement of Science. The NASA Medal for Exceptional Scientific Achievement, the NASA Public Service Medal, and the AGU Charles A. Whitten Medal are among the awards he has received. He has authored more than 200 refereed journal articles. He served as a member of numerous NASA committees and as a principal investigator for seven NASA missions.
In addition to his work with the GRACE mission, Tapley holds the Clare Cockrell Williams Centennial Chair in Engineering at The University of Texas, Austin and has served as director of the Center for Space Research since it was established in 1981. He joined the aerospace engineering faculty of The University of Texas at Austin in 1959 and served as the chairman of the university's combined Department of Aerospace Engineering and Engineering Mechanics from 1966 through 1977. He served as the Director of the Texas Space Grant Consortium from 1991 until 2004. His research interests include orbit mechanics, nonlinear parameter estimation, satellite data analyses and the uses of methods from these areas in satellite applications to studies of Earth and planetary system dynamics. A recent focus of his research has been directed at determining accurate models for Earth's gravity field.
GRACE is the Gravity Recovery and Climate Experiment. These twin satellites launched in March of 2002 are making detailed measurements of Earth's gravity field, which is leading to discoveries about gravity and Earth's natural systems. These discoveries are having far-reaching benefits to society and the world's population.
The primary goal of the GRACE mission is to accurately map variations in the Earth's gravity field. The GRACE mission has two identical spacecraft flying about 220 kilometers apart in a polar orbit 500 kilometers above Earth. Designed for a nominal mission lifetime of five years, GRACE is currently operating in an extended mission phase, which is expected to continue through at least 2015.
GRACE maps Earth's gravity field 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 Earth's gravity field with unprecedented accuracy. The results from this mission yield crucial information about the distribution and flow of mass within 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 ocean; and variations of mass within Earth. Another goal of the mission is to create a better profile of Earth's atmosphere. The results from GRACE make a huge contribution to NASA's Earth science goals, Earth Observation System and global climate change studies.
GRACE is a joint partnership between the NASA in the United States and Deutsche Forschungsanstalt fur Luft und Raumfahrt in Germany. In addition to Byron Tapley of The University of Texas Center for Space Research being its principal investigator, Christoph Reigber of the GeoForschungsZentrum Potsdam is the Co-Principal Investigator. NASA's Jet Propulsion Laboratory carries out project management and systems engineering activities.
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