Twin Probes to Investigate Space Weather Mysteries

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An artist's illustration of events on the sun changing the conditions in near-Earth space.

NASA

An artist's illustration of events on the sun changing the conditions in near-Earth space.

Late this summer, NASA plans to launch two very unusual weather satellites.

These satellites, known as the Radiation Belt Storm Probes (RBSP), won't be tracking cold fronts or thunderstorms on Earth. They'll be studying the weather in space.

Space weather doesn't usually get much attention ? until it makes trouble here on Earth.

That trouble starts when the sun ejects a massive cloud of particles and energy that heads toward our planet. When the cloud gets close enough, it begins to interact with the Earth's magnetic field.

The result can be radiation so intense it threatens anything in orbit.

"We have communication satellites, we have navigation satellites in space," says Barry Mauk of the Johns Hopkins Applied Physics Laboratory, the project scientist on the RBSP mission. "Those assets are strongly affected by radiation."

Satellites are especially vulnerable to highly energized electrons and protons that can "penetrate the boxes that comprise these spacecraft," Mauk says. "They can damage the circuitry. We have had failed spacecraft because of this space weather."

Space weather also can cause problems on the ground. Radio signals don't get through. GPS systems fail. Power grids go down.

And unfortunately, scientists aren't very good at predicting the impact of space weather.

One reason is a poor understanding of how solar storms affect the Earth's radiation belts, high-energy particles held in place by the earth's magnetic field, Mauk says. "Sometimes storms cause increases in radiation belts, sometimes they cause decreases in radiation belts, sometimes they have no effect at all," he says.

If scientists can solve this mystery, he says, predicting the impact of space weather could be more like predicting a hurricane's landfall.

But to study the problem, scientists need to see what's happening inside the radiation belts as a solar storm arrives. And that's where the new satellites come in.

They will be placed in an orbit that takes them through the radiation belts, says Jim Stratton, the mission systems engineer for the probes. Then, scientists will wait for a solar storm to arrive.

"When one of these big storms comes in, it can actually change and flex the magnetic field around the Earth," Stratton says. "So we'll measure that and then we'll see how all of that energy that's coming out of the sun deposits into the Earth's magnetic field, into the radiation belts."

Ordinary satellites wouldn't survive so much radiation. So Stratton and a large team at the Applied Physics Lab have spent years designing and building two very tough spacecraft.

Each of the spacecraft is an octagon about 4 feet tall. But once they are in space, they will deploy booms that extend about the length of a football field.

The probes are protected by heavy shielding that will keep radiation away from sensitive electronic components. And they are designed to preserve data gathered by onboard instruments even if radiation temporarily knocks out the computers.

"Most spacecraft try to avoid flying through the radiation belts because radiation is harmful," Stratton says. "We're going right into the middle of the environment."

The mission should improve their understanding of space weather, Mauk says. But it also may help explain the origin of mysterious radiation bursts in distant galaxies.

All of this depends on getting the probes into orbit and then coaxing them into precisely the right position, one following the other at a specified distance.

That's the responsibility of scientists in the Applied Physics Lab's mission control center. And fine-tuning an orbit is especially tricky when two satellites are involved, says Julia Andersen of the Mission Operations Team.

"Having two at the same time means you have to have two of everything," she says, including two separate "pits" in mission control that will accommodate two separate teams of scientists and technicians.

On launch day, those pits will be teeming with scientists and technicians who will take charge of the satellites once they leave the atmosphere, Andersen says.

"It's always fun knowing that you are in control of a spacecraft," she says.

Or in this case, two.

The probes are scheduled to launch from Kennedy Space Center on Aug. 23.

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