Right now, NASA’s Juno spacecraft is about 11 million miles from the planet Jupiter, moving at four miles per second. Jupiter’s massive gravitational pull is constantly "tugging" on the spacecraft, and once the vehicle reaches the planet, it will be going up to 40 miles a second. At that point, Juno will turn its engines on for 35 minutes to slow down and ultimately insert itself into orbit around Jupiter on July 4th. When that happens, it’ll mark the ninth time a spacecraft has explored the gas giant.

Juno is trying to figure out the origins of Jupiter

The main goal of Juno is to figure out the origins of Jupiter: when and how did it form? And how has it evolved over time? In an attempt to answer these questions, Juno will be closely analyzing Jupiter’s atmosphere. The amount of water and ammonia surrounding the planet can indicate which of Jupiter’s origin theories makes the most sense. The spacecraft will also be studying Jupiter’s magnetic and gravitational fields, to try to figure out if Jupiter has a solid core and how big that core might be.

Juno has nine on-board instruments, including a color camera called JunoCam that will get the best pictures ever of the planet’s polar regions. The spacecraft is also in a constant state of spin, which helps make the probe easier to control and ensures that all the instruments point at Jupiter once during each rotation. The spacecraft rotates about three times per minute, meaning all of Juno’s instruments will point at the planet 400 times every two hours, according to NASA.

The probe will follow a highly elliptical orbit that will take the spacecraft close to Jupiter's poles, in order to avoid the planet’s huge "radiation belts" — areas filled with charged particles that extend outward more than 400,000 miles into space. But for further protection, Juno is also encased in a special radiation vault.

With only a few weeks to go before Juno arrives at Jupiter, NASA scientists are looking over every aspect of their plan to insert the spacecraft into orbit. "Throughout the project, including operations, our review process has looked for the likely, the unlikely, and then the very unlikely," Rick Nybakken, a project manager for Juno, said in a statement. "Now we are looking at extremely unlikely events that orbit insertion could throw at us."

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