Voyager 2 launched toward the outer planets
On this day · 20 August 1977
On a rare planetary alignment, one probe set off to visit every giant world in our solar system.
On August 20, 1977, NASA launched Voyager 2 atop a Titan IIIE-Centaur rocket from Launch Complex 41 at Cape Canaveral, Florida. Confusingly, it left two weeks before its twin, Voyager 1, which took a faster route and overtook it.
The timing was no accident. A planetary alignment that recurs only about once every 176 years let mission planners chart a “Grand Tour,” using each planet’s gravity to slingshot the craft toward the next. Voyager 2 reached Jupiter in 1979, Saturn in 1981, Uranus in 1986, and Neptune in 1989.
It remains the only spacecraft to have flown past all four of the solar system’s giant planets.
Decades on, Voyager 2 still phones home from interstellar space, its radioisotope generators slowly fading. The faint signal now takes more than 19 hours to cross the void back to Earth.
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