Chocks away for NASA's Einstein test

Gravity Probe-B launch successful

By Lucy Sherriff, 21st April 2004

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NASA's Gravity Probe-B (GP-B) is being guided into a nearly perfect circular polar orbit 400 miles up, following its successful launch yesterday from Vandenberg Air Force Base in California.

Early reports from the Earth's newest satellite are good, according to Rex Geveden, the GP-B program manager: "The solar arrays are deployed, and we have received initial data that indicates all systems are operating smoothly. We are very pleased," he said.

The GP-B carries four of the most precise gyroscopes ever made, designed to test two predictions of Einstein's Theory of General Relativity: that space and time are warped by massive objects.

By watching how the near-perfect spheres spin, the US Space Agency hopes to see how the Earth warps space, and also whether the spin of the earth creates a drag in space-time. The spacecraft will be aimed constantly at a distant star. The spin axes of the on-board gyroscopes should drift minutely if the dragging effect occurs.

Following 60 days of calibration, the mission scientists will gather data on the precise spin-axis orientation of the gyroscopes. The probe will send data back at least twice a day for a year. When the mission finishes in 2005, NASA expects the analysis of the huge pile of data to take at least another 12 months.

"The Gravity Probe B space vehicle houses one of the most challenging science instruments ever devised and seeks to answer some of the most important questions about the structure of our universe," Geveden said.

Lead scientist on the mission, Stanford University's Dr. Francis Everitt, said: "This is...the outcome of a unique collaboration of physicists and engineers to develop this near-perfect instrument to test Einstein's theory of gravity". He described the successful launch as a great moment, and a great reponsibility. ®