Juno and Jupiter

NASA’s Juno spacecraft is on the final leg of its five-year journey to Jupiter. Yesterday, the Juno team completed the first of two maneuvers to line up its trajectory for a July 4th meetup. The spacecraft’s thrusters used up 1.3 pounds of fuel and changed Juno’s speed by just 1 foot per second (0.31 meters per second, or 0.68 miles per hour).

Juno launch

Juno’s journey to Jupiter began in 2011.

“This is the first of two trajectory adjustments that fine tune Juno’s orbit around the sun, perfecting our rendezvous with Jupiter on July 4th at 8:18 p.m. PDT,” said Scott Bolton, Juno’s principal investigator.

The next maneuver is planned for May 31, about one month before it enters orbit around the solar system’s biggest planet.

What’s different about Juno?

It’s solar powered. Nearly 19,000 solar cells attached to three 30-foot long solar arrays will generate the power needed to explore Jupiter.

Juno solar panels

“Juno is all about pushing the edge of technology to help us learn about our origins,” said Bolton. “We use every known technique to see through Jupiter’s clouds and reveal the secrets Jupiter holds of our solar system’s early history. It just seems right that the sun is helping us learn about the origin of Jupiter and the other planets that orbit it.”

Eight missions have traveled further than Juno. And all eight used nuclear power sources. Why can Juno get away with solar power instead of nuclear? There are a few different reasons.

One, solar-cell technology has improved. Despite being about 500 million miles away from the sun, Juno’s massive solar arrays will generate 500 watts. Rick Nybakken, Juno’s project manager, says that’s plenty.

“Juno is very efficiently designed, and it will be more than enough to get the job done,” said Nybakken.

Juno’s team is also placing the spacecraft in an orbit that avoids Jupiter’s shadow and maximizes the amount of sunlight it gets.

Last month, Juno officially broke the record for the longest distance traveled by a solar-powered spacecraft. On Wednesday, Jan. 13, Juno passed the 493 million mile mark, breaking the previous record held by ESA’s Rosetta spacecraft (492 million miles).

Juno infographic

Bolton downplayed the record saying, “the best is yet to come.”

Juno’s mission

Juno’s primary mission is simple but vital to understanding our solar system. Answer questions about Jupiter’s origins and its evolution into the gas giant we see today. We have a basic understanding of Jupiter’s formation, but the specifics elude us.

When exactly did Jupiter form? Did it form at its current orbit, or somewhere else and eventually settle where it’s at? How much water is in Jupiter’s atmosphere?

The water question will help scientists better understand how heavy elements were shifted around the solar system during its formative years. Plus, learning more about Jupiter will shed some more light on the hundreds of giant planets Kepler has discovered around other stars.

Juno will also take a much closer look at Jupiter’s colorful cloud bands and atmosphere. The spacecraft’s instruments will give scientists their first look at what lies beneath Jupiter’s swirling clouds.

Jupiter’s magnetosphere is another intriguing target for the Juno team. Inside Jupiter’s high-pressure atmosphere, hydrogen gas turns into a fluid called metallic hydrogen. This is what scientists believe is the source of the gas giant’s magnetic field. Juno will closely observe Jupiter’s magnetic fields near the poles and will watch auroras in ultraviolet.


Juno is the second spacecraft flying under NASA’s New Frontiers Program. New Horizons was the first and blew everyone away with breathtaking images of distant Pluto. Here’s to Juno being an even better follow up. It will reach Jupiter on July 4th and will orbit Jupiter 37 times over 20 months. In February 2018, its mission will come to a spectacular end as it falls through Jupiter’s atmosphere.

Image credits: NASA


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