|Voyager 1, traversing the heavens (NASA/JPL)|
The Voyager spacecraft were launched in 1977, at a time when the alignments of the outer planets would allow for a "Grand Tour" of the Solar System.
Voyager 1 traveled past Jupiter and Saturn, discovering volcanoes on Io and the thick atmosphere of Titan, before it was turned around to take pictures of the planets as it traveled beyond their orbits. The famous Pale Blue Dot picture was taken by Voyager 1 when it was over 40 times further from the Sun than Earth. Since that time, Voyager 1 has passed beyond the region of space where the solar wind from our star dominates over other stars; Voyager 1 is now an interstellar traveler.
Voyager 2, while not garnering as much fame as its twin, is the only spacecraft to ever flyby Uranus and Neptune. All of our best detailed information regarding those worlds and their moons comes from Voyager 2, which passed by Uranus in 1986 and Neptune in 1989. For instance, the odd surface of Neptune's moon Triton was revealed by Voyager 2, giving us the first hints that cryovolcanism is a process which occurs on the icy worlds of our solar system.
Recently, filmmaker Santiago Menghini has put together a short film highlighting the journeys of the Voyager spacecraft. Including photographs from the missions as well as sounds from the plasma frequencies of the planets, the film is a tribute to the successes of the Voyager mission. I highly recommend checking out the movie (below, or at Vimeo). Turn up your speakers' volume and full screen this one, you won't regret it.