Voyager 1

Voyager 1 launched on September 5, 1977, and used a faster trajectory to overtake its twin, making landmark flybys of Jupiter in 1979 and Saturn in 1980. Its cameras discovered active volcanoes on Jupiter’s moon Io — the first ever seen beyond Earth — and revealed the smoggy atmosphere of Saturn’s moon Titan, a choice of target that flung the spacecraft up and out of the plane of the planets.

In 1990, at Carl Sagan’s urging, Voyager 1 turned its camera homeward and captured the ‘Pale Blue Dot’ — Earth as a fraction of a pixel in a sunbeam. It crossed the heliopause into interstellar space in 2012, the first spacecraft to do so, and still whispers data home daily from more than 15 billion miles away on steadily dwindling plutonium power.