* Twin satellites to fly through Van Allen belts
* First detailed study of Earth's radiation belts
* Radiation impacts space weather environment around Earth
(Recasts with probes in orbit, adds quotes)
By Irene Klotz
CAPE CANAVERAL, Fla., Aug. 30 - An unmanned Atlas 5 rocket
lifted off on Thursday from Cape Canaveral Air Force Station in
Florida, placing a pair of heavily shielded NASA science
satellites into position to study Earth's radiation belts.
The 190-foot (58-meter) tall rocket, built by United Launch
Alliance, blasted off at 4:05 a.m. EDT (0805 GMT), soaring out
over the Atlantic Ocean toward an orbit as far as 19,042 miles
(30,645 km) above the planet's surface.
Riding atop the rocket were the identical twin Radiation
Belt Storm Probes, which are expected to spend two years
surveying the Van Allen radiation belts, hostile regions that
surround Earth and that most other spacecraft try to avoid.
"They're now at home in the Van Allen belts, where they
belong," deputy project scientist Nicola Fox told reporters
after the launch. "For the science team, the real work now
Named after University of Iowa physicist James Van Allen,
the two doughnut-shaped belts of trapped particles were
discovered in 1958 by Explorer 1, the first U.S. science
satellite. They are held in place by Earth's magnetic field,
which traps the electrically charged particles from the sun and
How the belts form and why they sometimes balloon out is a
Understanding the phenomenon is more than scientific
curiosity. Every spacecraft orbiting Earth, including the $100
billion International Space Station and its crew, fly through
the high-radiation regions, which can degrade solar panels and
"Modern society depends on satellites and other space-based
technologies ... making the research and understanding that will
come from (the probes) invaluable to building better protected
satellites in the future," New Jersey Institute of Technology
physicist Lou Lanzerotti said at a pre-launch news conference.
The satellites are expected to spend the coming two years
flying in tandem through the heart of the radiation belts. The
inner belt begins about 650 miles (1,046 km) above Earth and
extends to about 8,000 miles (12,875 km), but at times it can
dip as low as about 125 miles (201 km). The space station flies
about 250 miles (402 km) above the planet.
The outer belt begins at an altitude of about 8,000 miles
(12,875 km) and extends to about 26,000 miles (41,843 km).
The solar-powered probes, heavily shielded to operate in the
radiation belts, are flying in slightly different, highly
elliptical orbits that are inclined 10 degrees to the planet's
equator, allowing them to periodically lap each other. Science
operations are scheduled to begin after a 60-day instrument
The satellites, built and operated by Johns Hopkins
University's Applied Physics Lab, will fly as close as 100 miles
(161 km) to each one another, and as far as 24,000 miles (38,624
The dual measurements are key to understanding how the belts
puff out and contract over time and in response to solar
"If you imagine sitting on a life raft in the ocean and you
suddenly go down and come up again, you don't know very much
about what caused you to go down and come up," Fox said before
"If you have a friend who is sitting on a life raft a little
way away, you can say 'Well, did we both go down and up at the
same time?' In which case it's a big-scale feature like a
tsunami. Did one of us go down and then the other one? You can
really start to look at the global dynamics of what's happening
in the radiation belts," Fox said.
United Launch Alliance is a partnership of Lockheed Martin
and Boeing. The mission cost $686 million,
including the launch vehicle.
(Editing by Louise Ireland, Tom Brown and Paul Simao)