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ALL SYSTEMS GO: Flight director
Jerry Aguinaldo of Lockheed (left) and Colin Perry
of NavAstro are among numerous scientists tracking
GP-B's progress in orbit.
Linda Cicero |
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.”
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