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JPL scientists watch anxiously as Juno probe nears Jupiter

Forget fireworks this July 4th.

The most exciting celestial show this Independence Day is happening more than 400 million miles from Earth.

Right around sunset Pacific time, NASA's Juno spacecraft is scheduled to pass through a cloud of extreme radiation circling Jupiter to reach orbit around the largest planet in our solar system.

If that sounds risky, rest assured — it is.

At any moment in that perilous journey, energized particles traveling near the speed of light could strike key parts of the Juno probe, endangering its mission of surveying the gas giant for clues about how it formed.

For instance, just one of those energized particles could cause a glitch in the electronics forcing the spacecraft to reboot just as it was supposed to fire its rocket and insert into orbit.

"In order to go into orbit around Jupiter you have to fire the rocket at the right time," explained Steven Levin with NASA's Jet Propulsion Laboratory and a project scientists for Juno.

Fire the rockets too late and it can throw the entire process off, he said.

Over the long term, Jupiter's intense radiation field could degrade Juno's circuits and microchips, ruining key scientific gear and limiting the data NASA can gather.

To give the spacecraft a fighting chance against so much cosmic chaos, Levin and his team have placed the bulk of the electronics in a titanium vault.

"That was a new idea for Juno," he explained. In the past, NASA simply shielded important gear from radiation, but in this case, all of it was bunched into a protective space about the size of a college dorm fridge.

Most of the spacecraft's electronics are protected from Jupiter's intense radiation field with this tank-like titanium vault.
Maya Sugarman/KPCC
Most of the spacecraft's electronics are protected from Jupiter's intense radiation field with this tank-like titanium vault.

The engineers also designed the system so it could withstand a glitch or two, Levin said.

"But obviously... it's our first time through the environment, we'll all be a little nervous."

So, the risks are great, but so are the rewards.

Even though Jupiter is massive enough to fit all the other planets in our system inside it, we still know very little about how it was born.

Understanding where Jupiter came from is important since it was most likely the first planet formed after the sun, and it influenced how the rest of the solar system developed.

"What we are really looking for is the recipe of how you make planets, how you make a solar system," said Scott Bolton, Juno's principal investigator.

One looming questions Juno hopes to answer is what lies at the heart of the planet. Is it all gas? Or does it have a rocky core that formed first, providing the structure for the rest of the materials to gather around?

This could help us understand what materials were available for the rest of the planets as they grew.

Juno is set to analyze the deep structure of Jupiter for clues.

It'll also study the famous storms on the gas giant. For example, Jupiter has a large swirling cloud structure, dubbed "the great red spot." It's twice as wide as Earth and is believed to have been blowing furiously for more than a hundred years.

Bolton said we don't know how deep storms like that go. Are they skin deep or do they penetrate far into the planet's center?

 "In order to learn about those things you have to get really close to Jupiter with very sensitive instruments, and we've never really done that before," he said. 

Juno may also bring us the first pictures of Jupiter's poles.

Juno's camera has thick glass pieces protecting the sensor from Jupiter's intense radiation field. With this camera, each pixel will represent 15 kilometers.
Maya Sugarman/KPCC
Juno's camera has thick glass pieces protecting the sensor from Jupiter's intense radiation field. With this camera, each pixel will represent 15 kilometers.

Monday's orbital insertion comes after five years and hundreds of millions of miles of travel. Early on, the spacecraft got an assist by looping around the inner solar system and swinging by Earth to get a speed boost from our gravity field.

It's solar powered with an array of panels about the size of a city bus, but when it reaches its target, it will be so far from the sun that the massive panels will only be able to generate about 400 watts, said Doug Bernard, an engineer on the project.

About half of that energy will be used just to keep the spacecraft from freezing.

During the insertion into orbit, all non-essential equipment will be shut off so the craft can focus its energy on the rockets. The bulk of the scientific gear will be turned on later.

Once it's circling Jupiter, Juno will fly incredibly close, coming within 3,100 miles of the planet's cloud tops. When the probe finishes 33 planned science orbits, it will have covered the entire planet.

But first, NASA needs that risky orbital insertion on July 4th to go as planned.

It'll happen a little after 8 pm PT, as many firework shows on the West Coast will be starting.

Juno scientists, engineers and their families will be gathered at the JPL campus in Pasadena, eagerly awaiting signals from the probe.

Even if everything works out, don't expect any celebratory fireworks from that neck of the woods. Those aren't allowed near JPL's labs, explained Steve Levin.

“So, no sparklers,” he laughed.

"I think most of us will breathe a big sigh of relief, and then say 'OK, let's move on to the next thing,'" he said. 

For those looking for a big boom though, the Rose Bowl will be celebrating Juno during its 4th of July fireworks show.

There will be a special firework signed by members of the team and the golf course area will even feature artwork of the spacecraft to commemorate its daring mission.