Twin probes designed to explore the outer solar system, Pioneer 10 and 11 would become two of just five spacecraft destined for interstellar space. Originally built as a back-up to Pioneer 10, Pioneer 11’s mission was expanded when Pioneer 10 launched successfully in March 1972. With Pioneer 10 on a path to a December 1973 encounter with Jupiter, Pioneer 11 could be turned to a more daring polar flyby at the gas giant, as well as exploration of Saturn.
Pioneer 11 launched April 5, 1973, arriving at Jupiter in December of 1974 and successfully mapping its polar regions. Jupiter’s gravity slingshotted Pioneer 11 toward Saturn, and it became the first spacecraft to fly by Saturn in September of 1979. While there, Pioneer 11 discovered two new moons and a new ring.
Pioneer 11 crossed Neptune’s orbit in 1990, and sent its final transmission in 1995. Pioneer 10, Pioneer 11, Voyager 1 and 2 , and New Horizons are all on various stages of their journey out of our solar system, but in case of future interactions far from home, both Pioneers carry gold plaques with messages of peaceful greeting, in part crafted by Carl Sagan.
