Machine Design

NASA probe checks on Einstein

Four ultraprecise gyroscopes aboard NASA's Gravity Probe B satellite are gathering data to test Albert Einstein's nearly 90-year-old General Theory of Relativity.

Gloved hands holding an encased flight gyroscope rotor.


The spacecraft, which has been orbiting the Earth for more than 17 months, downloaded 50 weeks' worth of data to computers in the Mission Operations Center at Stanford University. Scientists are now analyzing the data, which is expected to take a year.

"This has been a tremendous mission for all of us," says Francis Everitt, Gravity Probe B principal investigator at Stanford. "With all the data gathered, we are proceeding deliberately to ensure everything is checked and rechecked."

Launched on April 20, 2004, from Vandenberg Air Force Base, Calif., Gravity Probe B's spherical gyroscopes precisely measured two extraordinary effects predicted by Einstein's Theory. One is the geodetic effect, the amount by which the Earth warps the local space time in which it resides. The other, called frame dragging, is the amount by which the rotating Earth drags local space time with it.

Stanford conceived the experiment and is NASA's prime contractor for the mission. The university has the lead for data analysis. Lockheed Martin Space Systems Co., Sunnyvale,Calif., designed, integrated, and tested the space vehicle, and built some major payload components.

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