Voyager 1 launched in 1977 has been traveling through the heliosheath surrounding our solar system for the last 8 years and is expected to cross the heliopause within the next year or two into interstellar space. NASA scientists didn't think that Voyagers (1 & 2) would last this long, but they're still operating though many of their instruments are shut down.
“…NASA had planned the original Voyager Mission to coincide with a once-every-175-years alignment of Jupiter, Saturn, Uranus, and Neptune that would allow the two spacecrafts to use the planets' gravity to “swing” them from one planet to the next. This technique minimized the need for extra propulsion and travel time….”
