UNO gets to Jupiter by flying by the Earth. It gains momentum by passing the Earth at five hundred kilometers altitude and in doing so it gets sucked into the Earth's gravity well
and what happens is that the trajectory which is on a path relative to the sun originally, now is flying by the earth and is also influenced by the earths gravity field.
It gets deflected out towards the planet Jupiter. The idea is that you can't get there directly unless you have a much bigger launch vehicle.
When we get to Jupiter we do a big maneuver called JOI.
The Jupiter Orbit Insertion Maneuver is what actually puts us into an orbit about Jupiter so that we're captured by Jupiter's gravity.
It needs to be a big maneuver because we're flying at this enormous velocity around the sun and in order to be captured by even a big planet like Jupiter
we have to aid that capture by doing a big maneuver to slow us down.
There's so little time to react that we have to let it do its own thing and just trust that the planning and the testing that went into that will do the right thing.
We plan on actually listening in on the spacecraft as it does its Jupiter Orbit Insertion
and at the very end we have it radio back to tell us OK, we did all the right things, here's how the spacecraft is doing, we survived.