Voyager and Jupiter. Animation of the Voyager spacecraft flying past the planet Jupiter. Voyager 1 and 2 are twin space probes launched by NASA in 1977 to study the outer Solar System and eventually interstellar space. Voyager 1's closest approach to Jupiter was on March 5, 1979, at a distance of about 349, 000 kilometres. Voyager 2's closest approach occurred on July 9, 1979. It discovered rings around the planet, as well as volcanic activity on the moon Io.