Juno, too, will be subjected to an enormous amount of radiation — the equivalent of 100 million dental X-rays. That level of radiation can fry a spacecraft's electronics in an instant, and may have been among the reasons that Jupiter missions were initially passed over in NASA competitions to obtain launch approval.
Then, in the late 1990s, Bolton was working on Cassini-Huygens, the first spacecraft to go into orbit around Saturn.
One morning — after spending the previous day in a series of meetings about measuring radiation in deep space — Bolton was standing in the shower. He had an epiphany.
He would need a specific instrument loaded onto Juno — a microwave radiometer, which could probe the planet's atmosphere with less interference. The spacecraft would also need to orbit Jupiter's poles, not its equator, thereby reducing the information "noise" that would come from the planet's radiation belts.
The combination, he believed, would yield the first solid reading of water and oxygen on Jupiter. It would be a critical step in understanding the distribution of heavy elements during the formation of the planets. There would be implications far beyond our solar system; hundreds of "Jupiter-class" planets have been discovered in recent years in further reaches of the galaxy.
"The rest is history," Bolton said.
To complete such a promising and demanding set of calculations during its orbits, Juno will fly little more than 3,000 miles above Jupiter's poles, far closer than any spacecraft has ever managed.
Engineers have equipped it with a protective titanium box, 500 pounds and roughly three square feet, to shield what engineers call Juno's brain and heart — its data components and the electronics that control its power and send its science back to Earth. Chodas said Juno is essentially "an armored car in space."
"Now we just have to wait five years until we get to Jupiter," Bolton said. "You have to have a lot of patience in this business."