Voyager 2 lifted off aboard a Titan-Centaur rocket, sixteen days before its twin Voyager 1, on a trajectory exploiting a rare planetary alignment. Over the next dozen years it became the only spacecraft to visit Uranus and Neptune, returning images that rewrote textbooks on the outer solar system before heading into interstellar space.
Engineers timed the launch to catch a once-every-176-years planetary alignment that let Voyager 2 use gravity assists to visit all four gas giants in a single mission. Despite being launched second, it was placed on a slower path so it would still reach Jupiter before its sibling craft's flyby data could be fully analyzed, a piece of orbital choreography that took years of planning.
The spacecraft carried the Golden Record, a phonograph disc etched with greetings in 55 languages, whale songs, and music from Bach to Chuck Berry, intended as a message to any spacefaring civilization that might one day find it. Voyager 2's cameras delivered the first close-up portraits of Uranus's tilted magnetic field and Neptune's Great Dark Spot in 1989.
It remains, alongside Voyager 1, one of the farthest human-made objects from Earth. In December 2018 it crossed the heliopause into interstellar space, and its plutonium power source still trickles enough electricity to keep a handful of instruments alive, transmitting data from over 12 billion miles away on a radio signal that takes more than 18 hours to reach home.