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Earth Surface & Interior

Since 1994, global GPS network (GGN/IGS) analysis at JPL has consistently delivered high accuracy satellite orbits, station positions and velocities, Earth rotation parameters, atmospheric water vapor, and ionospheric total electron content. These products have enabled scientific discoveries and monitoring capabilities, with contributions to plate tectonics, rheology, angular momentum exchange, and surface mass redistribution. GGN provides an accurate (<1 cm) reference frame for NASA's low Earth orbiting platforms used to monitor global change in sea level, the ice sheets, and the water cycle. GGN analysis is broken into two steps: (1) estimation of GPS orbits, clocks, and global parameters using only a ~80 subset of stations, followed by (2) precise point positioning of stations using products from the first step. While much valuable science at the regional scale can be achieved by step (2), the accuracy of global-scale parameters is inherently limited by step (1). The reason for this two-step approach relates to "carrier phase biases". The computational required to resolve all the integer ambiguities in these biases scales to the fourth power of number of stations. In the current system, 400 stations would take 600 times longer to process than for 80 stations. We have developed a new algorithm to resolve ambiguities that scales linearly with number of stations. A ~400-station network can be resolved in 30 minutes on a desktop PC. As currently implemented, the technique works at step (2) described above. We propose to implement it at step (1) of JPL's GGN system, to enable global analysis of ~400 stations. This vast increase in sampling will result in improved IGS products across the board. Once developed, the technique will be implemented operationally at JPL, making the improved products available to NASA missions, Earth scientists, IGS, and the IERS.

Project PI: Geoffrey Blewitt/University of Nevada, Reno

Nevada Bureau of Mines and Geology/ Seismological Laboratory Mail Stop 178 University of Nevada Reno, Nevada 89557

Phone: (775) 682-8778

Fax: (775) 784-1709

Email: gblewitt@unr.edu

http://www.nbmg.unr.edu/staff/geoff.htm

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Started: Aug 09, 2010

Last Activity: Dec 10, 2010

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