After 12 years of orbiting Saturn, NASA's Cassini spacecraft is preparing to enter a new orbit that will explore the planet's rings. Cassini will be nearly 5,000 miles of Saturn’s F ring, which marks the border of the main ring system. By coming in such close proximity with the planet, Cassini will be able to study particles and gas molecules that linger near the rings and observe small moons around the planet. After that, Cassini will perform a death plunge into Saturn’s atmosphere on September 15, 2017, bringing its long mission to an end.