Trajectory of the Voyager probes, illustration. Voyager probe (lower right) with the flight paths of NASA's two unmanned Voyager probes sent to the outer planets. A rare alignment of these giant planets meant it would be possible to visit them all in one mission. Voyager 2 (orange line) left Earth in August 1977, and Voyager 1 (yellow line) launched two weeks later with a faster trajectory. They both encountered Jupiter (1979) and Saturn (1980/1981), but only Voyager 2 encountered Uranus (1985) and Neptune (1989). The probes beamed back the first close-up images of these planets, and vast amounts of scientific data. The probes have exceeded the solar system's escape velocity, and continue to beam back data as they head out into interstellar space.