NASA's Radiation Belt Storm Probes are flying in Earth orbit after a successful liftoff and ascent this morning. The probes launched aboard a United Launch Alliance Atlas V rocket at 4:05 a.m. EDT after a smooth countdown at Cape Canaveral Air Force Station in Florida. The probes were released from the rocket's Centaur upper stage one at a time and sent off into different orbits, kicking off the two-year mission to study Earth's radiation belts.

"I'm very happy to report that we have two happy spacecraft on orbit," said Rick Fitzgerald, RBSP project manager from the Johns Hopkins University Applied Physics Laboratory, which is managing the mission for NASA. "Many thanks to ULA and Launch Services Program for getting us on orbit, giving us a great ride and injecting us in exactly the orbit that we wanted to be in."

During the RBSP mission, the identical twin spacecraft will fly in separate orbits throughout the inner and outer Van Allen radiation belts that encircle the Earth. The sun influences the behavior of the radiation belts, which in turn can impact life on Earth and endanger astronauts and spacecraft in orbit.

"Today, 11 years of hard work was realized by the science team as a number of us stood together watching the rocket lift off the pad," said Nicky Fox, RBSP deputy project scientist from APL. "(The spacecraft) are now at home in the Van Allen belts where they belong, and we can all finally breathe out now that solar panels are out on both of them."

The spacecraft will go through a 60-day commissioning period before beginning its prime mission.

"Now that the spacecraft are safely in orbit, the real fun begins," said Mike Luther, deputy associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. "After the commissioning period, we get to then begin to perform the most detailed study of Earth's radiation belts that's ever been undertaken."