Voyager 1 and 2

Launched in 1977, the twin Voyager probes are humanity's most distant emissaries, with Voyager 1 crossing into interstellar space in 2012 and currently over 15 billion miles away. They achieved the Grand Tour of Jupiter, Saturn, Uranus, and Neptune, discovering 24 new moons and active volcanism on Io. This mission is 50% lighter in mass than the average interplanetary probe but has operated for 46 years, outpacing #3 Hubble Space Telescope in longevity. Voyager 2 remains the only spacecraft to visit ice giants, a data point unmatched through 2025.