Voyager 2

Voyager 2 launched on August 20, 1977 — 16 days before its faster twin — onto the only trajectory that could line up flybys of all four outer planets within a single mission. Over twelve years it returned humanity's first close-up views of Jupiter (1979), Saturn (1981), Uranus (1986), and Neptune (1989), then continued outward into the heliosphere. On November 5, 2018, it became the second spacecraft to cross into interstellar space. Despite operating ~20 billion kilometres from the Sun on aging hardware, Voyager 2 still returns plasma, magnetic-field, and cosmic-ray data via NASA's Deep Space Network.

Identical bus design to Voyager 1: 3.7-metre high-gain antenna, three RTGs, magnetometer boom, and plasma, cosmic-ray, ultraviolet, and infrared spectrometer instruments. Voyager 2 still has a working Plasma Science instrument (Voyager 1's failed in 1980), making it the only craft directly measuring interstellar plasma density. Each carries the same Golden Record. The craft is heading southward out of the ecliptic plane, opposite Voyager 1, giving researchers two complementary probes of the heliosphere's shape.

Voyager 2 remains the only spacecraft ever to visit Uranus and Neptune. Its 1986 Uranus flyby revealed 11 new moons and a magnetosphere tilted bizarrely sideways; the 1989 Neptune flyby captured the Great Dark Spot, the moon Triton's nitrogen geysers, and rings invisible from Earth. After Neptune, the mission rolled into the Voyager Interstellar Mission. In 2020 NASA upgraded the DSS-43 dish in Australia — the only antenna powerful enough to send commands to V2 — restoring two-way communication after a planned 11-month hiatus.