An Atlas V rocket on the launch pad at Cape Canaveral (Getty)
Cape Canaveral, FL (written by James Dean/Florida Today) -- A two-year mission to study Earth's Van Allen radiation belts is under way after a successful launch Thursday morning from Cape Canaveral Air Force Station.
Twin NASA probes were deployed about 80 minutes and 90 minutes after their 4:05 a.m. blastoff atop a United Launch Alliance Atlas V rocket, prompting cheers from the launch team.
It was the third attempt to launch the $686 million Radiation Belt Storm Probes mission, after scrubs last Friday and Saturday.
A smooth countdown culminated in the 189-foot rocket rumbling from Launch Complex 41 at the opening of a 20-minute launch window.
The rocket quickly disappeared into a low bank of clouds above the pad before emerging as a bright streak of orange light in a night sky shared by a nearly full moon.
The rocket's first stage and payload fairing separated about four minutes into flight, and the Centaur upper stage then completed two engine burns on either side of a nearly hour-long coast.
The two spacecraft -- for now named RBSP-A and RBSP-B -- will study how the radiation belts respond to solar storms.
They're equipped with extra armor to shield electronics and sensitive instruments from bombardment by highly charged particles.
Better understanding of the Van Allen belts could help protect spacecraft and astronauts that fly through them, as well as assets on the ground.