Originally published on Medill News Service.
An artist’s depiction of the Juno spacecraft nearing Jupiter, NASA.gov.
After fifteen years, 1.7 billion miles and an intense 35-minute engine burn, Juno has made it into orbit around Jupiter.
Monday at 9 a.m. PDT NASA held a press briefing at the Jet Propulsion Laboratory (JPL) in Pasadena, California, where anxious scientists prepared for what would hours later become a defining moment in their careers. “It’s a milestone for planetary science,” said Jim Green, NASA director of planetary science, in his opening statement. Scientists’ aim for this mission is to unravel the mysteries of Jupiter’s core, study its magnetosphere and gain insight into the origins of our solar system.
The Juno mission is riddled with aerospace firsts and milestones, including operating “further from the sun than any other solar-powered mission in history,” said Rick Nybakken, Juno project manager. The spacecraft also faces unparalleled obstacles, which required the top minds in astrophysics and engineering to develop the exacting maneuvers of Monday’s Jupiter Orbit Insertion (JOI).
One of the biggest challenges faced by scientists was getting the spacecraft through Jupiter’s intense radiation fields. Jupiter, like Earth, has radiation belts that emanate from its north and south poles. However, “Jupiter’s are on steroids, they are a very serious hazard,” said Green.
A diagram showing Juno’s journey through the different intensity zones of Jupiter’s radiation rings. A screenshot from NASA’s Jupiter Orbit Insertion (JOI) briefing Monday morning at the Jet Propulsion Laboratory in California.
“These are high energy electrons that are so energetic, they are moving at the speed of light,” said Heidi Becker, Juno radiation monitoring investigation lead. “They will go right through a spacecraft and strip the atoms apart inside your electronics.” Becker compared the radiation Juno faced to “something equivalent to a human being having 100 million x-rays in less than a year.”
An illustration of Juno's electronics vault, designed to protect the craft from severe radiation damage. A screenshot form NASA's JPL JOI briefing.
To combat this intense radiation from damaging Juno’s vital electronics, scientists placed the craft’s technologies inside a central vault made of titanium walls that are ½ inch thick. The vault offers significant protection; however, it does not block the full force of Jupiter’s radiation. The craft will still be deteriorated by radiation particles, but at a much slower rate, allowing it enough time to complete its two-year mission.
To minimize Juno’s exposure to Jupiter’s most intense radiation zones, scientists designed a unique polar orbiting route that goes extremely close to the planet, passing from its north to south pole. “At the closest position to Jupiter, we are only only a few thousand miles above the cloud tops,” said Dr. William Kurth, lead co-investigator for the Radiation Belt Storm Probes Waves Investigation and the Juno Waves Investigation. The closeness of the orbit sends the craft out on an elongated elliptical journey, passing the planet every 53 days, though after an additional engine burn later this year, the orbit will be shortened to 14 days.
Juno’s elliptical polar orbit around Jupiter. A screenshot from NASA’s JPL JOI briefing.
Another obstacle faced during Juno’s JOI was passing through Jupiter’s ring of debris. The spacecraft was at risk of incurring serious damage if it ran into a meteorite, or, at that speed, even dust. “But we are built like an armored tank,” said Green. And the small probability of making contact with the debris turned out to be in Juno’s favor. The JOI target was a space of tens of kilometers wide, and the craft “hit it within 1.2 seconds after a journey of 1.7 billion miles. That tells you just how good our navigation team is,” said Nybakken.
The space craft entered its polar orbit as planned and without conflict at 8:53 p.m. PDT, to the relief of the mission’s team and to the thrill of the world.
“We always get excited here at the Adler Planetarium with these kinds of missions, because it raises the awareness of space science,” said Dr. Andrew Johnson, vice president for Astronomy and Collections at Chicago’s Adler Planetarium. “It is an opportunity for everybody out there to connect with space.”
And people have indeed been connecting—the Juno mission currently has 358,000 Twitter followers, and counting. You can follow the mission on Twitter or Facebook for updates as Juno progresses. Juno will be orbiting close to Jupiter again next month, when the craft will take its first close-up images of the planet to share with the world.