Voyager

NASA / JPL

Two probes within NASA's Mariner program, headed for Jupiter and Saturn, evolved into the Voyager probes. Like Pioneers 10 & 11 they were powered by a Star-37E solid rocket motor, which would propel them beyond the solar heliopause.

Voyager 2 launched on a Titan IIE rocket on August 20, 1977. It flew by the Jupiter, Saturn, Uranus and Neptune systems and reached solar escape velocity. On November 5, 2018 it passed 122 astronomical units and entered interstellar space.

Voyager 1 left earth 16 days after Voyager 2 on September 5, 1977. It flew by Jupiter, Saturn and its moon Titan. On August 25, 2012 it was the first spacecraft to pass heliopause (120 AU) and enter interstellar space, 6 years before Voyager 2.