Juno Ready to Launch to Jupiter

The Juno spacecraft will soon be on its way to Jupiter on a mission to look deep beneath the planet's swirling curtain of clouds to find out what lies beneath. The answer might confirm theories about how the solar system formed, or it may change everything we thought we knew.

"The special thing about Juno is we're really looking at one of the first steps, the earliest time in our solar system's history," said Scott Bolton, the principal investigator for the Juno mission. "Right after the sun formed, what happened that allowed the planets to form and why are the planets a slightly different composition than the sun?"

Starting the 4-ton spacecraft on its five-year journey to the largest planet in the solar system is the job of a United Launch Alliance Atlas V equipped with five solid-fueled boosters. Even with that much power, Juno will still require a flyby of Earth to get up enough energy to swing out to Jupiter.

With three 34-foot-long solar arrays and a high-gain antenna in the middle, the spacecraft is reminiscent of a windmill. It even spins slowly as it goes through its mission. Those arrays will be the sole power source for Juno as it conducts its mission, a first for a spacecraft headed beyond the asteroid belt between Mars and Jupiter.

The Atlas V has proven a reliable option for NASA's Launch Services Program, or LSP, the organization that oversees NASA launches and chooses the best launchers for different spacecraft.

"It's flown 28 times, pretty challenging missions, pretty challenging payloads," said Omar Baez, launch director for Juno. "It's got a heritage that goes back to the Atlas I in some of the components and in the upper stage, so it's an evolution of a family in its current configuration and shape and form. I'd say it's pretty robust."

The spacecraft is to lift off at 11:34 a.m. on Aug. 5 from Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida. The mission faces a limited launch window to get off Earth before Jupiter's orbit took it out of alignment.

"Juno only has a 22-day launch window, or else we're down for another 13 months until our next opportunity," said John Calvert, mission manager for Juno. "So it's those kinds of challenges with making sure you do all the little things necessary to maximize the opportunities you get for those 22 days."