Juno has travelled about 3 billion kilometres to get to Jupiter, launching in August 2011, performing an Earth flyby in October 2013 and arriving at the planet on 4 July 2016.
The spacecraft will now begin orbiting the gas giant on a path that will take it over the planet’s poles.
It will take 14 days to complete each orbit and will do so 37 times over the course of the mission, flying low over Jupiter’s cloud tops as close as 4,100km from the surface.
Juno is the first solar-powered spacecraft designed to operate so far from the Sun. Because Jupiter’s orbit is five times farther from the Sun than Earth’s, the planet receives 25 per cent less sunlight, but Juno has been equipped to face this challenge with three solar panels that extend outward to give the spacecraft an overall span of 66 feet.
A time-lapse movie of the Galilean moons orbiting Jupiter, as seen by Juno during its approach. This movie begins 12 June 2016 and ends 29 June. Credit: NASA/JPL-Caltech/SwRI
Ultimately, the mission will seek to collect data to improve our understanding of how both Jupiter and the Solar System were formed and how they evolved.
Jupiter is an important planet for astronomers and cosmologists because of its relatively massive size, as learning more about giant planets can help us understand the exoplanets and planetary systems currently being discovered beyond our own.
Juno will attempt to determine how much water is in Jupiter’s atmosphere, which will tell NASA scientists a lot about how the planet formed, and it will also measure the temperatures, cloud motions and composition of its atmosphere.
It will spend time analysing Jupiter’s magnetic and gravity fields and exploring its magnetosphere, which will reveal information that will help scientists determine the planet’s interior structure.
One of Jupiter’s key properties is its designation as a ‘gas giant’.
The planet is made mostly of hydrogen and helium, meaning it must have formed early enough to capture those elements left over from the formation of the Sun.
How this happened is unclear, and Juno’s analysis of Jupiter should help NASA better understand the history of its formation.
The next few months will see the team preparing Juno for its main mission, carrying out final tests and checks on its analytical apparatus, but also conducting preliminary science.
“Our official science collection phase begins in October, but we’ve figured out a way to collect data a lot earlier than that,” says Juno principal investigator Scott Bolton, “which when you’re talking about the single biggest planetary body in the Solar System is a really good thing.
There is a lot to see and do here.”
“With Juno, we will investigate the unknowns of Jupiter’s massive radiation belts to delve deep into not only the planet’s interior, but into how Jupiter was born and how our entire Solar System evolved,” says NASA administrator Charlie Bolden.
Juno is due to orbit Jupiter for the next 20 months, before deorbiting into the planet in February 2018.