Either of two unmanned U.S. interplanetary probes launched in 1977 to gather information about the Sun's outer planets.
Voyager 1 flew by Jupiter in 1979 and reached Saturn in 1980. Voyager 2 traveled more slowly, flying by Jupiter, Saturn, and Uranus to reach Neptune in 1989. Data and photographs from both probes revealed new details about these giant planets, their moons, and their rings. In 1998 Voyager 1 became the most distant human-made object in space (overtaking Pioneer 10). Both Voyagers were expected to remain operable through the first or second decade of the 21st century, periodically transmitting data on the heliopause .