3-2-1: The probe at launch. Courtesy Boeing

“Weather is green. Spacecraft is green.”

Stanford scientists had been waiting some 45 years to hear those words from a NASA launch director. Gravity Probe B, the $700 million experiment to test Einstein’s general theory of relativity, had endured decades of hard work, technical setbacks and congressional threats to terminate funding. High shear winds had scratched a launch the day before. But on April 20, the probe finally was ready for takeoff.

At 9:57:23.734 a.m. Pacific time, GP-B rumbled off the launchpad at Vandenberg Air Force Base in Southern California. On campus, hundreds of scientists, engineers, students and their families roared their approval at a closed-circuit television broadcast in Cubberley Auditorium. Machinist Aldo Rossi, who has been fine-tuning the spacecraft for almost 10 years, pumped the air as it streaked across a picture-postcard sky aboard a Boeing Delta II rocket, bound for a 400-mile-high polar orbit. “It’s crazy,” Rossi told his wife. “Just crazy.”

Cheer after cheer went up from the Cubberley crowd in the first few seconds of launch as six rockets were jettisoned, followed by another three. An hour into the flight, the spacecraft deployed its solar arrays to harness the sun’s
energy to power some electrical systems, and the experiment was primed for what principal investigator Francis Everitt, watching on the ground at Vandenberg, called “truly a new venture in fundamental physics.” In the experiment, four small quartz gyroscopes—the most perfectly round objects ever created—spin thousands of times per minute in a huge thermos-shaped vacuum chamber as they point at a faraway guide star, IM Pegasi. A slight change in direction of the gyroscopes will confirm the theory that Earth’s gravity distorts the fabric of space.

After thoroughly checking and calibrating instruments in the initialization and orbit checkout phase, researchers will spend the next 12 months collecting science data, and another year analyzing it. Controllers for the joint venture between Stanford, nasa and Lockheed Martin are communicating with the orbiting spacecraft from the Missions Operations Center on campus.

Electrical engineering professor Brad Osgood was squinting as he emerged from Cubberley into the sunlight of a glorious April morning. “I don’t know anyone personally involved in the project,” he said. “But it’s such a fantastic story that I certainly wanted to be there.”