NASA’s Juno Mission Is About to Perform Its Most Dangerous ManeuversPosted: July 4, 2016
Jennifer Ouellette reports: NASA’s Juno spacecraft has been spinning through space on its way to Jupiter for five years and 445 million miles, and now it’s less than 10 hours away from entering the gas giant’s orbit—the equivalent of a single rotation of Jupiter. If all goes well, scientists will finally be able to learn what lies beneath Jupiter’s turbulent atmosphere, examine its impressive magnetosphere, and possibly determine the composition of its core.
“If Juno gets hit even by a small piece of dust, it can do a great bit of damage,” he said. “We believe probability is incredibly low that Juno will hit dust or debris, but it’s not zero. Even a 10 micron particle could do some damage moving at the speed we’re moving.”
— Juno project manager Scott Bolton
But first, it’s going to have to execute a tricky 35-minute engine burn under the harshest conditions any NASA spacecraft has yet faced. And that has Juno mission scientists on edge today. They’ve modeled every scenario they can think of, and planned for every contingency. But as Juno project manager Scott Bolton said in this morning’s briefing at the Jet Propulsion Laboratory in Pasadena, “This is the highest risk phase.”
“We’ve done everything humanly possible to make this mission a success, but it’s still a cliffhanger,” said Jim Green, director of planetary science at NASA headquarters in Washington, DC.
Thus far, the mission has gone off without a hitch, but plenty could still go wrong. For instance, what if the main engine doesn’t fire on cue to start the burn, so far from the sun? “We’ve fired the main engine twice successfully and the third time should be a charm,” said Rick Nybakken, Juno project manager. “But this is the first time we’ve ever fired the main engine at Jupiter. It’s make or break for us.”
Then there’s the intense radiation from Jupiter’s enormous magnetosphere. According to Heidi Becker, lead investigator for Juno’s radiation monitoring, this translates into millions of high energy electrons moving near the speed of light. “They will go right though the spacecraft,” she said. “It’s the equivalent of 100 million x-rays in less than a year for a human being if we had no protection.”
Juno’s polar orbit will avoid the worst of the radiation belts at the planet’s equator, but other high-intensity regions are unavoidable. This exposure could easily fry Juno’s electronics, which is why they are housed in solid titanium radiation vaults with walls half an inch thick.
Juno will start to experience that radiation fairly early in the orbital insertion maneuver. Towards the middle of the burn is another dangerous phase, because the gas giant also has a ring of debris around it, similar to the Van Allen Belt that surrounds Earth. At this point Juno will be traveling at very high speeds and its engine doors will be open and vulnerable, according to Bolton….(read more)