Voyager 1

Voyager 1 is one of two spacecraft in NASA's Voyager program. It launched from Cape Canaveral, Florida, on 5 September 1977, after its twin Voyager 2. The numbering reflects the intended encounter sequence, not launch order: Voyager 1 followed a faster trajectory and passed Voyager 2 later that year. The original mission called for close studies of Jupiter and Saturn, their rings and their larger moons.

The mission took advantage of a favorable alignment of the outer planets that allowed spacecraft to use gravity assists: a close flyby changes a probe's speed and direction, helping it travel to another destination with less propellant than a route relying only on onboard propulsion. Voyager 1's path after Saturn sent it outward toward the boundary of the Sun's solar-wind bubble, rather than onward to Uranus and Neptune; Voyager 2 visited those planets.

Voyager 1 flew past Jupiter in March 1979 and Saturn in November 1980. Its instruments and images expanded knowledge of both planets and their satellite systems. Among the most consequential Jupiter results was the observation of active volcanoes on Io, the first active volcanism seen beyond Earth. The mission also identified previously unknown features of Jupiter's rings and moons.

At Saturn, Voyager 1 examined the planet's rings and atmosphere and made a close flyby of Titan. The probe's course was chosen to pass close to Titan, whose atmosphere was of particular scientific interest; this trajectory took it away from the remaining outer planets. The later Voyager 2 encounters at Uranus and Neptune were therefore a separate extension of the twin mission, not part of Voyager 1's route.

On 25 August 2012, Voyager 1 crossed the heliopause, the outer boundary of the heliosphere—the region shaped by the solar wind and the Sun's magnetic influence. NASA describes this milestone as the spacecraft's entry into interstellar space. The distinction matters: the heliopause marks a change in the surrounding environment, not a sharp edge to every part of the Solar System's gravitational domain.

After the crossing, measurements from Voyager 1 and its twin have provided direct information about plasma, magnetic fields and energetic particles beyond the heliosphere. Voyager 1's passage beyond the heliopause does not mean it has passed the most distant gravitationally bound region of the Solar System: NASA places the distant Oort Cloud far beyond the heliopause, and Voyager is not expected to reach it for centuries.

Voyager 1 was built for a much shorter planetary mission, but its robust systems and careful operations have allowed it to work for decades. It is powered by radioisotope thermoelectric generators, which convert heat from radioactive decay into electricity. Their output gradually declines, so engineers shut down equipment in a planned order to conserve power while preserving high-value measurements.

On 17 April 2026, NASA's Jet Propulsion Laboratory reported turning off Voyager 1's Low-Energy Charged Particles experiment (LECP) to help keep the mission operating. The instrument had measured low-energy charged particles since launch and contributed data about the interstellar medium. NASA's mission reporting describes Voyager 1 as continuing to return scientific information from interstellar space; its available science changes as power and instrument systems age.

Voyager 1 carries a 30-centimetre gold-plated copper phonograph record, as does Voyager 2. NASA describes it as a time capsule intended to communicate a selection of Earth's life and culture to any extraterrestrial finder. The record contains sounds and images, and its protective cover includes instructions for playing it and locating Earth. It was a symbolic payload rather than an instrument for the spacecraft's scientific observations.