"We have a nice clean jettison of the fairing," said launch commentator Marc Lavigne as the protective nose cone fell away from Gravity Probe B, exposing it to space.
With only a one-second window for liftoff, the spacecraft and its Delta 2 roared away from the launch complex at California's Vandenberg Air Force Base exactly at 12:57:23.734 p.m. (1657:23.734 GMT). Launch officials missed the tiny launch window on April 19 because of complications due to wind conditions. That launch was scrubbed, and a previous April 17 date was also pushed back to hardware glitches on the launch pad.
"This, of course, is a wonderful time for us at Stanford," said Francis Everett, principle investigator of the project at Stanford before the launch. "It's great to be beyond the point of building the spacecraft."
It took about 11 minutes for the first two stages of the 13-story Delta 2 to push Gravity Probe B into space. After coasting for about an hour, the rocket's second stage conducted a brief burn, then cast the probe off on a 16-month journey in polar orbit 400 miles (644 kilometers) above Earth.
The Gravity Probe B mission is a collaboration between NASA and Stanford researchers to test two principles predicted by Einstein's theory of relativity, both of which deal with the Earth's effect on space and time. The first, called the "geodetic effect," is the warping of space and time due to the Earth's presence. The second, dubbed "frame dragging," is the amount that the Earth pulls the space and time around it as it moves through the universe.
"It's hard to imagine a simpler experiment," Everett said, adding that the spacecraft keep itself pointed at a guide star for reference. "We have a star that we're pointing at and these spinning spheres to test the principles."
Housed in a thermos filled with liquid helium, the four ping pong shaped gyroscopes will be spun up to 10,000 revolutions per minute (RPM), then monitor how that spin direction is affected by Einstein's predicted principles.
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