Juno at Earth 
Earth is about to be robbed. A spacecraft that’s on its way to Jupiter will swing past Earth tomorrow. It’ll “steal” a bit of momentum from the home planet, giving it the final boost it needs to reach its destination.
Such a maneuver is known as a gravity assist, and it’s quite common. It makes it possible to reach the outer planets with less fuel, allowing a craft to use a smaller booster rocket, which cuts costs. It also makes it possible for a craft to maneuver between moons in a planetary system, allowing it to conduct far more close-range observations.
This encounter is with Juno, which was launched two years ago. It’ll swing about 300 miles above Earth’s surface, which will increase its speed by more than 16,000 miles per hour. Earth will actually slow down as a result of the encounter. But since our planet is about a million million billion times heavier than the spacecraft, we won’t notice a thing.
When Juno arrives at Jupiter in July of 2016, it’ll enter orbit around the planet’s poles — something that no craft has ever done before. That will allow it to probe Jupiter’s magnetic and gravitational fields in detail. From those readings, scientists will learn more about the planet’s structure. Current ideas say that Jupiter consists of a dense, rocky core surrounded by layers of hydrogen and helium. Juno’s observations should help confirm that picture — providing a look deep into the heart of the solar system’s largest planet.
Script by Damond Benningfield, Copyright 2013