CAPE CANAVERAL, Florida (AP) ― Twin U.S. satellites rocketed into orbit Thursday on a quest to explore Earth’s treacherous radiation belts and protect the planet from solar outbursts.

It’s the first time two spacecraft are flying in tandem amid the punishing radiation belts, brimming with highly charged particles capable of wrecking satellites and endangering astronauts.

“We’re going to a place that other missions try to avoid, and we need to live there for two years. That’s one of our biggest challenges,” said Richard Fitzgerald, project manager for Johns Hopkins.

These new satellites, shielded with thick aluminum, are designed to withstand an onslaught of cosmic rays for the next two years.

Scientists expect the $686 million mission to shed light on how the sun affects the Van Allen radiation belts, named after the astrophysicist who discovered them a half-century ago.

Earth’s two doughnut-shaped radiation belts are full of high-energy particles from the sun and elsewhere in the cosmos, trapped by Earth’s magnetic field.

Normally, the belts remain well above the International Space Station and low-flying satellites. But the belts can expand during solar storms into the paths of orbiting spacecraft. If severe enough, the storms can cripple satellites and endanger astronauts and disrupt power and communications on the ground.

The goal of this mission is to improve space weather forecasting.

“The Earth responds to what’s coming from the sun, so we say, `If the sun sneezes, the Earth catches a cold,’” said Nicola Fox, deputy project scientist for Johns Hopkins. The symptoms vary widely and need to be better understood, she said.

Science instruments aboard the nearly identical spacecraft will measure the high-energy particles coursing through the radiation belts and numbering in the trillions.

Fox said the beauty of having two satellites is that scientists will see whether energy disturbances affect just one or both, allowing for measurements over space as well as time.

Jupiter, Saturn, Uranus and Neptune also have magnetic fields and radiation belts. While the processes are understood, mysteries abound. Fox likens it to making a cake: “You know all the ingredients but you’re not quite sure of the proportions of each piece in each given storm.”

James Van Allen’s 1958 discovery of the radiation belts are said to be the first scientific discovery of the Space Age.

It took NASA three tries to launch the spacecraft. Last week’s attempts were thwarted by trouble with a tracking beacon on the Atlas V rocket and then stormy weather. NASA chose to wait until the passage of Hurricane Isaac before trying again.