What is Juice?
Jupiter is the largest planet in our solar system. We have confirmed 95 moons orbiting it, the four most massive ones being Io, Europa, Ganymede, and Callisto. Io is an extremely volcanic moon, while the rest have a crust of ice.
Now, JUICE stands for JUpiter ICy moons Explorer. The name ten billion percent gives away all the mission's secrets! This spacecraft will fly all the way to Jupiter, collecting tons of data from it and its big three icy moons! While Juice will eventually settle around Ganymede, NASA is also preparing Europa Clipper, which focus on Europa and is set to launch October next year.
The ESA has a fancy PowerPoint slide explaining the basics of Juice: the ESA Juice Launch Kit.
Timeline
To get to Jupiter, it's not enough to just throw our rocket in its direct path and wait. To reach our destination in a reasonable time frame, we'll need to use what's known as gravity assists.
Basically, you take advantage of a celestial body's gravity. It will pull on the spacecraft, and depending on how you leave, you can change the craft's speed and orbit! (Remember: gravity is written in m/s2—speed per second.) For our purposes, we'll need to speed it up and throw it around just right so it eventually lands in Jupiter's orbit path.
Juice will perform flybys of Earth and our Moon, then Venus, and then Earth again twice. Once it's all done, it's full speed ahead to Jupiter! This whole process will take eight years, which is already double the 3.5 year actual mission time.
Problems
Despite our fancy tools, you should remember that space is ruthless. The smallest mistake unaccounted for could mean the death of the mission. And two days ago, Juice had a problem deploying its antenna.
But it's not over just yet. Don't underestimate space engineers! They're a creative bunch. Since it's still moving (albeit very slowly), they think that something just got stuck, and a little nudge should be able to fix it.
We might be able to get off easy this time, but eight years leaves a lot of room to go wrong. Let's just hope it all goes according to plan.
The End of Juice
Eventually, Juice will settle into an orbit around Ganymede, where it'll stay for another 3.5 years. After that, it'll crash and the mission will be over. However, it won't die in vain. Humanity will receive tons of new data about the Jupiter system, including whether or not it can support life, bringing us one step closer to becoming an interplanetary species.
And for that I say...
Get excited!!