In 1977, NASA launched two probes designed to last five years. Voyager 1 and 2 are now the only human-made objects in interstellar space, still operating, still transmitting, funded by a team of engineers some of whom have worked on the mission for nearly 50 years

NASA launched Voyager 2 on 20 August 1977 and Voyager 1 on 5 September. The spacecraft were built for a five-year mission to Jupiter and Saturn. Almost 49 years later, NASA still lists both probes as active, receiving commands and returning data from beyond the heliosphere.

The scale of that extension deserves careful wording. NASA funds the mission, while the Jet Propulsion Laboratory operates it. The Voyagers are the only spacecraft ever confirmed to have operated outside the heliosphere, which is the operational meaning of interstellar space used by the agency.

They have not left every part of the solar system.

Five years covered Jupiter and Saturn

The original assignment was narrower than the mission people now remember. According to NASA’s Voyager fact sheet, each probe was designed for close studies of Jupiter and Saturn, Saturn’s rings and the planets’ larger moons. Five years was enough for that two-planet programme.

A rare alignment made a longer route possible. The gravity of each planet could bend and accelerate a spacecraft towards the next one, reducing the need for onboard propellant. Voyager 1 took a close route past Titan that sent it out of the planetary plane. Voyager 2 retained the geometry needed to continue to Uranus in 1986 and Neptune in 1989 after NASA approved additional funding.

The five-year design life was therefore real, but it was not a timer programmed to stop the spacecraft. Redundant hardware and remote reprogramming gave the mission room to continue.

Interstellar does not mean beyond the whole solar system

Voyager 1 crossed the heliopause in August 2012. Voyager 2 followed in November 2018. The heliopause is the outer boundary of the heliosphere, the bubble formed by the solar wind and the Sun’s magnetic influence.

Beyond that boundary, the probes can directly measure the nearby interstellar environment. NASA therefore describes them as the only spacecraft ever to operate in interstellar space.

This does not mean they have passed the solar system’s most distant comet reservoir. The Oort Cloud extends vastly farther from the Sun. The more exact claim is that Voyager 1 and 2 are the only working spacecraft known to have crossed the heliopause.

Both spacecraft are still transmitting

NASA’s status page, last updated on 14 July 2026, lists two working science instruments on Voyager 1: its magnetometer and plasma wave subsystem. Voyager 2 has those two instruments plus its cosmic ray subsystem.

The radios, computers and attitude-control systems needed to keep the high-gain antennas pointed towards Earth must also remain alive. A command takes roughly 23 hours to reach Voyager 1 and about 19 and a half hours to reach Voyager 2. Diagnosing a problem can therefore consume nearly two days before a reply returns.

Operating is not the same as operating unchanged.

Longevity now depends on subtraction

Each probe uses three radioisotope thermoelectric generators that convert heat from decaying plutonium-238 into electricity. Their output falls by about four watts per spacecraft each year.

The mission has responded by turning off heaters, backup systems and science instruments. In April 2026, engineers shut down Voyager 1’s low-energy charged-particle instrument after almost 49 years of operation. NASA said the decision should buy about another year while the team develops further power-saving changes.

The aim is not to preserve every original capability. It is to keep enough power for communication and at least one useful measurement for as long as the ageing hardware allows.

The people form a mission across generations

The final clause in the headline needs the same precision as the spacecraft claims. NASA has documented engineering work that began nearly 50 years ago and continues today, but that does not establish that current engineers have all served since launch.

Project manager Suzanne Dodd began her Voyager career while Voyager 2 was approaching Uranus, making the 1986 encounter her first job after college. NASA reported in 2024 that retired early-mission personnel still return to help younger engineers understand hardware and software built decades before some of them were born.

Ed Stone provides the cleanly documented 50-year tenure. He served as Voyager project scientist from 1972 to 2022, but he was a physicist rather than an engineer and died in 2024.

The continuity is institutional as much as individual. JPL preserves old records, consults retired specialists and teaches new staff how to command machines designed under assumptions that no longer fit the length of the mission.

NASA believes the probes may retain at least one operating science instrument into the 2030s, but it also warns that an unexpected fault could end either mission sooner. For now, both are still answering.