AP
This artist's rendering made available by NASA/JPL-Caltech on July 7, 2015, more
Most Americans will look to the skies July 4 to see fireworks. But nervous scientists will hope for a heavenly spectacle of a different sort: the arrival of an enormous spacecraft at Jupiter.
“Someone asked when does the nail-biting start. It’s already started,” Juno principal investigator Scott Bolton of the Southwest Research Institute told reporters Thursday. “Jupiter is the most extreme planet we have, and we’re going right next to it.”
Jupiter, by far the largest planet in the solar system, makes a great big target compared to a shrimp like Pluto. But it is by no means easy company for a spacecraft. The fifth planet from the sun has the strongest magnetic field and the fastest spin of any of the planets, Bolton said.
Most dangerous of all, radiation levels around Jupiter are “the scariest … of any place in the solar system,” said Heidi Becker of NASA’s Jet Propulsion Laboratory. Engineers had to equip Juno with a special “radiation vault” made of titanium walls a half-inch thick. Weighing 400 pounds empty, it will protect the spacecraft’s delicate electronics from radiation exposure equivalent to what a human patient would receive from 100 million dental X-rays in one year, Becker said.
If there’s too much radiation at Jupiter, there’s also too little sunlight, or at least not enough to power the spacecraft using ordinary gear. So Juno is tricked out with three enormous solar panels stretching nearly 30 feet long each, which will harvest the trickle of sunshine that makes it all the way to Jupiter’s neighborhood.
Though huge, the spacecraft is agile. It will “cartwheel through space,” Bolton said, at a rate of twice a minute, giving each sensor a chance to peer at the planet. That prevents the need for elaborate pointing and steering of the craft.
Juno will look for a rocky core buried deep inside Jupiter’s thick layer of gases. The existence of such a core would mean that Jupiter took shape after rock began forming in the rest of the solar system, Bolton said.
The spacecraft will also look for the roots of Jupiter’s clouds and the long-standing storm known as the Great Red Spot. And it will help scientists understand how the planet grew and evolved.
But exploration has a price, and Juno, though stoutly armored, cannot survive the onslaught of radioactive particles forever. Leaving it in orbit around Jupiter forever is not an option. Scientists fear it could contaminate Jupiter’s moon Europa, one of the solar system’s most hospitable spots for living creatures and a potential target for another NASA mission.
So in early 2018, Juno will go out in glory: it will take a final dive into Jupiter and burn up.