Only spacecraft to visit all four outer planets
Launched 16 days before its twin, Voyager 2 took a slower trajectory that allowed it to visit all four outer planets — Jupiter (1979), Saturn (1981), Uranus (1986), and Neptune (1989) — providing humanity's first close-up views of the ice giants. It crossed the heliopause in November 2018 and is the only probe to have returned in-situ measurements from both hemispheres of the heliosphere.