Voyager 2 was the first spacecraft to fly past Neptune, making its closest approach on August 25, 1989.
NASA launched Voyager 2 in 1977 to study Jupiter and Saturn, but a carefully planned trajectory allowed it to continue toward Uranus and Neptune. Its Neptune encounter completed the first close investigations of all four giant planets by one spacecraft.
Voyager 2 returned images and measurements of Neptune’s atmosphere, rings, moons, magnetic field, and winds. It discovered new details about the planet’s active weather, including the Great Dark Spot observed during the encounter. The spacecraft also flew close to Neptune’s largest moon, Triton.
Voyager 1 followed a different trajectory after Saturn and did not visit Uranus or Neptune. Voyager 2 remains the only spacecraft to have visited both of those outer planets. Its continuing interstellar mission began after the planetary encounters.