WEBVTT

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 Gravity Probe B. or GPB. was a mission designed to test two predictions of Einstein's general theory of relativity. 

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 GPB. containing the world's most precise gyroscopes. spent 17 months collecting data while in orbit around the Earth. 

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 Unlike most NASA science missions that seek to make new observational discoveries. GPB was conducted to verify 

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 fundamental assumptions in physics. which have implications for all of space exploration. 

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 The GPB spacecraft launched from Vandenberg Air Force Base. California. 

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 atop a Boeing Delta II rocket at 9:57 a.m. Pacific Time on April 20. 2004. 

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 The solar arrays deployed on schedule. and the Boeing Delta II launch vehicle second stage released the spacecraft 

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 in a circular polar orbit so precise. that no orbit trim or correction was required. 

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 Scientists have analyzed the data since October 2005. and expect to report findings in 2011. 

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 After completing operations. Gravity Probe B was successfully decommissioned on Dec. 8. 2010. 

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 The spacecraft will continue to circle the Earth in a polar orbit at an altitude of 400 miles. 

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