A NASA mission to test two predictions of Albert Einstein's Theory of General Relativity is in orbit and operating as planned, officials said Friday. This image shows the Gravity Probe B satellite launching aboard a Delta 2 rocket from Vandenberg Air Force Base in California on April 20.

The probe is orbiting 400 miles above Earth, and all spacecraft systems are performing well, officials said. The satellite's solar arrays are generating power, and all electrical systems are powered on and communications with ground control are normal

Soon the real work begins.

Also known as GP-B, the probe will use four ultra-precise gyroscopes to test Einstein's theory that space and time are distorted by the presence of massive objects -- essentially that gravity warps space-time. The mission will measure how space and time are warped by the presence of the Earth, and how the Earth's rotation drags space-time around with it.

Credit: NASA/MSFC