The twin spacecraft were launched from Cape Canaveral, Florida, with no special destination in mind. Unlike many of the other missions that aimed for the moon or a specific planet, the Voyagers were sent on flybys to planets on their way out to the furthest reaches of the solar system — and beyond. Along the way, they took careful observations of the outer planets, helping to expand our understanding of them.

On this day, August 25, in 1981, almost four years to the day after its launch and nine months after its twin flew by, the Voyager 2 made the closest approach ever to Saturn — within 100,000 miles, near enough to probe the upper atmosphere with radio link.

Voyager 2’s observations allowed scientists to determine that Saturn’s upper atmospheric temperature (a balmy -333) and pressure, as well as the composition of elements: Saturn apparently contains a lot of helium. The real reason for the close approach, however, was to use the planet’s gravity as a slingshot to send Voyager 2 to its next destination — Uranus.