Are We There Yet? Juno Set for July 4 Rendezvous With Jupiter

The Juno orbiter will be used to study how the gas giant Jupiter evolved

A NASA spacecraft is on track to rendezvous with Jupiter after a nearly five-year journey.

The space agency said Thursday the encounter between Juno and Jupiter will occur on July 4. That's when Juno will fire its main engine to slow down and slip into orbit around the biggest planet in the solar system.

Juno launched from Cape Canaveral in August 2011 on a long and increasingly strange trip that will put the orbiter through a harrowing approach to Jupiter. NASA and the Jet Propulsion Laboratory in Southern California even produced a Hollywood-style trailer to illustrate the perils that await.

The spacecraft will fire its main engine to slow down, then move into place to begin its orbit around the fifth planet from the sun.

It will be a delicate, precisely calculated celestial dance.

"It's a one-shot deal," mission chief scientist Scott Bolton from the Southwest Research Institute in San Antonio, Texas, said Thursday. "Everything is riding on it."

Once in place, Juno will begin circling Jupiter's poles and peering through clouds to study how the planet formed and evolved. Unlike Earth, which is a rocky planet, Jupiter is a gas giant made up mostly of hydrogen and helium.

"Jupiter is a planet on steroids," Bolton said. "Everything about it is extreme."

Previous missions to Jupiter have relied on nuclear power sources this far out from the sun. Juno is unique because it has solar panels that are designed to face the sun during most of the mission.

It will orbit the planet for 20 months — that's 37 times around — before ending its mission in February 2018. After all that, the orbiter will simply burn up as it soars toward the planet's surface. 

Juno's instruments are protected from radiation by a titanium vault. It also is equipped with a camera, which should provide stunning views if previous missions are any indication. 

Previous Jupiter visits showed its signature Great Red Spot, a long-lived storm, and its many moons.  The Galileo mission dropped a probe on the planet's surface and conducted 14 years of exploration. 

But many questions remain, such as whether Jupiter has a solid core and how much oxygen and water are present. 

The Associated Press contributed to this report.

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