The NASA Gravity Probe B (GP-B) Relativity Mission has successfully mated its science payload to its spacecraft and after successful systems testing, the GP-B space vehicle was shipped to Sunnyvale, Calif., on Feb. 9, 2002, to prepare for upcoming rigorous environmental tests.

The Gravity Probe B spacecraft on a modal stand in preparation for environmental testing. Photo: Lockheed Martin

"These milestones are a huge accomplishment for this dedicated team," said Gravity Probe B program manager Rex Geveden, of NASA's Marshall Space Flight Center in Huntsville, Ala. "The Gravity Probe B team is working hard to complete preparation and testing of one of the most unique experiments ever attempted in the history of science."

Gravity Probe B, led by principal investigator Francis Everitt and program manager Sasha Buchman of Stanford University in Stanford, Calif., has been pushing the limits on many different technological fronts, including gyroscope technology, materials science, metrology, astrometry, and cryogenics.

Scheduled for launch in late 2002 and using highly advanced technology, GP-B is expected to be the most precise test to-date of two extraordinary predictions of Albert Einstein's Theory of General Relativity.

Using its space-bound gyroscopes in a drag-free polar orbit, GP-B will measure how space and time are warped by the presence of the Earth, and, more profoundly, how the Earth's rotation drags space-time around with it. These effects have far-reaching implications for the nature of matter and the structure of the Universe and are considered among the most profound enigmas of physics.

The mission's science instrument and its components were developed, designed, built and integrated in Stanford University's Hansen Experimental Physics Laboratory. The payload is made up of the science instrument inside a probe integrated into one of the largest flight dewars (thermally insulated containers) ever constructed. The dewar provides the extremely low temperature environment needed for proper operation of the experiment while in Earth orbit.

The team has spent the last eight months in payload testing, successfully verifying all subsystems and the integrated payload at Stanford University before transporting and then mating the payload to the Lockheed Martin spacecraft at the corporation's nearby facility in Palo Alto. Systems testing was conducted there to begin preparations for the series of acoustic and thermal-vacuum tests in Sunnyvale that will qualify the GP-B space vehicle for its upcoming launch.

Development of the Gravity Probe B mission is the responsibility of Stanford University, with major sub-contractor Lockheed Martin Corporation.

GP-B is managed for NASA by the Marshall Space Flight Center.