On a clear August day in 2011, NASA launched a cube perched atop an Atlas V rocket that unfurled into a probe the size of a basketball court, complete with three whirling solar arrays.
That probe, named Juno in honor of the Roman god Jupiter’s wife, embarked on the first mission to map the mysterious inner workings of the largest planet in our solar system. The extraordinary five year journey involved a push through the inner solar system, a slingshot around the sun, a flyby of Earth and ultimately a capture by Jupiter’s gravity.
When Juno fires its main engines July 4, the journey will end as it slips into orbit above Jupiter. But the mission to explore what lies beneath the swirling clouds of gas will have just begun.
Excitement about the mission has been building in the scientific community — NASA’s website already has a countdown — and is just now spreading to the general public. Juno even has its own twitter account (@NASAJuno) with nearly a quarter-million followers.
Jupiter protects us from big cosmic collisions by taking hits and flinging things out of our solar system with its gravity. Without it, things would be much more chaotic. We need to understand how that works.
Bob Bonadurer, Milwaukee Public Museum
The Independence Day firing is critical; a reverse thrust generated during the burn will essentially slam on the brakes so the probe can skim over Jupiter and into a stable orbit. NASA expects to receive confirmation of the start of Juno’s engine burn at 8:18 p.m. and should know whether it worked by 8:53 p.m.
On July 4, Paul Borchardt, observatory director at the Milwaukee Astronomical Society in New Berlin, will eagerly be awaiting online mission updates for Juno.
“This is one of the fastest objects mankind has ever built,” Borchardt said, “and now NASA has to slow it down and bring it into orbit. If they don’t, the mission ends. If they do, then the real science begins.”
With its enormous magnetic field, Jupiter creates one of the brightest auroras ever observed despite being composed mostly of ammonia, hydrogen and helium. In some respects, Jupiter and its dozens of circling moons functions as almost a miniature solar system. Some astronomers even consider Jupiter a failed star.
Juno will be the first spacecraft to complete its orbits over Jupiter’s poles. Here, it will escape the brunt of the planet’s intense radiation and provide the first data from the uncharted regions from which the magnetic field emanates.
“Juno will go where no spacecraft has gone before — deep into the harshest radiation environment in the solar system outside the sun,” Rick Nybakken, Juno Project Manager from NASA’s Jet Propulsion Laboratory, explained during a recent news conference.
In November, public can vote for features that will get a close-up look
In an effort to prolong Juno’s survival, NASA housed the probe’s sensitive equipment in a 1 1/2-inch-thick titanium vault that cuts the radiation exposure by 800 fold.
Scott Bolton, Juno’s principal investigator, described the incredible efforts to ensure mission success. “Jupiter is the most extreme planet we have, and we are going right next to it. It’s got to do the extreme.”
Bob Bonadurer, director of theater and planetarium at the Milwaukee Public Museum, said people don’t realize how important the gas giant is to Earth.
“Jupiter protects us from big cosmic collisions by taking hits and flinging things out of our solar system with its gravity. Without it, things would be much more chaotic. We need to understand how that works.”
Incredibly high pressures and temperatures within Jupiter make the elements inside do some physically weird things. Specifically, scientists think the brutal conditions inside Jupiter force hydrogen into a fluid state, called “metallic hydrogen,” which is capable of conducting electricity.
By studying the charged particles and gravitational pull in the upper atmosphere, NASA will be able to determine whether metallic hydrogen is responsible for Jupiter’s powerful magnetic field. It should also reveal how deep the planet’s characteristic orange and white bands extend and if a solid core might be hidden at the center.
Moreover, scientists expect data from Juno to answer key questions about planetary formation and the origins of our solar system. Because Jupiter has a large mass, it has absorbed countless impacts from asteroids and comets unscathed and has retained the most intact material since the birth of the sun.
Each orbit will take 11 days, with Juno tracking different paths across Jupiter with its instruments and camera, JunoCam. Because Jupiter also will be rotating on its own axis, the entire planet will be surveyed inside and out by the end of the 37 planned orbits.
NASA expects the probe to survive Jupiter’s radiation onslaught through October 2017. At that point, the sensors will have endured radiation as strong as 100 million dental X-rays.
The first images should be publicly available at the end of August. Once the initial data is collected from the scientific instruments, NASA will point JunoCam at specific features to get more detailed images and then upload the photographic data in real time.
That is where NASA needs your help.
In November, voting will open for the public to choose which of these features will receive a close-up. The options range from the famous Great Red Spot where a storm has been raging for centuries, to a line of white storms known as the String of Pearls, to the planet’s north pole.
NASA expects the probe to survive Jupiter’s radiation onslaught through October 2017, by which time Juno’s sensors will have taken countless measurements and images. At that point, the sensors will have endured radiation as strong as 100 million dental X-rays.
That’s when the mission will end for Juno, which will be directed to plunge into Jupiter’s cloud tops and burn up like a meteor.
It will also be the end for the probe’s passengers: three spacecraft grade aluminum LEGO characters in the likenesses of Jupiter, Juno and Galileo. NASA included the figures on board in hopes of engaging children in scientific discovery and teaching them to “always reach to the stars.”