The twin Voyager spacecraft, over the course of a dozen years, drew back the curtain on nearly half of the solar system. From launch in 1977 through the spectacular parting shots of Neptune at the outer reaches of the solar system in 1989, this pair of spacecraft explored four planets -- Jupiter, Saturn, Uranus and Neptune -- as well as dozens of moons, and the rings and magnetic environments of those planetary systems.
The Voyagers were designed to take advantage of a rare geometric arrangement of the outer planets that occurs only once every 176 years. This configuration allows a single spacecraft to swing by all four gas giants without the need for large onboard propulsion systems; the flyby of each planet both accelerates the spacecraft and bends its flight path. Without these gravity assists, the flight time to Neptune would have been 30 years.
The second of the two Voyager spacecraft, Voyager 2, was launched first, on 20 August 1977. It was followed on 5 September 1977 by Voyager 1, which was put on a faster, shorter trajectory to Jupiter. Both launches took place from the Cape Canaveral Air Force Station in Florida.