We're in the MOC. That’s Mission Operations Center, for you earthlings.
We’ve recently emerged from IOC, or initialization and orbit checkout, and are now “in science,” the phase of the experiment where precise data collection begins. We’re standing in a room filled with computer consoles that are plugged into NASA ground networks. Batches of time-tagged commands have just been sent to a spacecraft that’s orbiting 400 miles above earth, and all eyes in pods Delta and Echo are on their screens. Watching for, say, another South Atlantic anomaly.
“This is where we fly the spacecraft,” mission director Brett Stroozas says, beaming at the multitude of whiz-bang instruments. Even the clock on the wall, which looks workaday, has specialized functions, including the capacity to pinpoint MET, or mission elapsed time. “It gives us a quick snapshot of what’s happening,” Stroozas explains.
The second-floor room in the Gravity Probe-B building, just off Campus Drive and across the street from the Hansen Experimental Physics Laboratory (HEPL), is the nerve center for a $700 million science experiment 40 years in the making. Designed to test Einstein’s general theory of relativity, GP-B has been guided from its lightbulb-moment infancy, through a fitful, congressionally-stalled adolescence, to its adult launch by principal investigator Francis Everitt, a research professor at HEPL.
Although Everitt has been the driving force behind GP-B since 1962, he wears a simple blue badge when he enters the MOC: “It means I’m allowed into the room, but not allowed to touch anything.” The coveted green badge, which authorizes its wearer to run the controls, belongs to Stroozas, who previously worked on NASA’s Extreme Ultraviolet Explorer satellite. GP-B is a collaborative effort between NASA, Lockheed Martin and the University that has involved hundreds of undergraduate students over the decades and launched scores of graduate dissertations.
Everitt hosted a celebratory bash at his Portola Valley home last summer after it became clear that the 3-ton spacecraft had zeroed in on guide star HR 8705 (IM Pegasi) and was on target for the experiment, which is expected to last about two years. These days scientists are closely monitoring four niobium-coated, chilled quartz gyroscopes the size of ping-pong balls that are spinning up to 10,000 revolutions per minute in a quartz housing inside the spacecraft. The gyros, which are designated the roundest objects ever manufactured in an upcoming issue of the Guinness Book of World Records, are attached to an all-glass telescope. If the tiny balls deviate from their original spinning axes, even a slight shift will tell researchers that Einstein had it right—Earth’s gravity distorts the fabric of space.
Launched in April, the spacecraft and its delicate research package required more fine-tuning than anticipated. To get to the stage where the satellite could begin to collect data, the telescope had to be aligned properly with the guide star, and the gyros had to be spun up to full speed, compensating for air drag and solar radiation pressure. In all, mission specialists at Stanford beamed more than 70,000 commands to the ship. “You plan for what you expect, and then you get up there and find a whole different set of things you never expected,” says Stroozas. “That’s what makes IOC so interesting, and so much fun.” Everitt, on the other hand, looks back at the intricate adjustments that had to be made after the launch and is pleased that the ramp-up period finally came to a close: “I sigh with relief that it’s over.”
Using a scale model of the spacecraft, Everitt points to the various shields and baffles that prevent sunlight from getting into the dewar, the giant thermos bottle that holds a cigar-shaped vacuum chamber containing the telescope and gyros. Some 645 gallons of superfluid helium surround that probe, keeping the instruments inside it stable at near-zero temperatures. “The total amount of heat going into the dewar is 120 milliwatts, or 1/30th the amount of heat put out by a cheap flashlight bulb,” Everitt says. Keeping the experiment super-cooled in space, he adds, “is not a simple job.”
In the coming months, as the spacecraft orbits the earth every 97 minutes and 37 seconds, the GP-B flight director and other specialists will be uploading commands and monitoring what happens as the experiment is in eclipse, and out of eclipse. And they’ll be keeping their eyes on that all-important wall clock. As Everitt and his team analyze data from the spinning gyroscopes, they’ll be digging into the enigma of gravity—and the structure of our universe. “But we’re just too busy to reflect on it now,” he says. “One doesn’t get much time for introspection.”
