Under this plan, Voyager 2’s science instruments will be on for several years longer than previously anticipated, allowing even more exploration from interstellar space.

Launched in 1977, the Voyager 2 spacecraft is more than 12 billion miles (20 billion kilometers) from Earth, using five science instruments to explore interstellar space. To keep these vehicles operational despite the reduced power supply, the legacy spacecraft began using a small reserve power store that was separated as part of the onboard safety mechanism. The move would allow the mission to delay the shutdown of the science instrument until 2026 instead of this year.

Turning off the science instrument does not complete the task. After one instrument shuts down in 2026, the probe will continue to operate with all four science instruments until power dips require the other to shut down. If Voyager 2 stays healthy, the engineering team thinks the mission could potentially take many years.

Voyager 2 and its twin Voyager 1 are the only spacecraft to operate outside the heliosphere, the protective bubble of particles and magnetic fields created by the Sun. The probes are helping scientists answer questions about the shape of the heliosphere and its role in shielding Earth from energetic particles and other radiation found in the interstellar medium.

“The science data that the Voyagers send back becomes more valuable the further they get from the Sun, so we’re definitely interested in keeping as many science instruments as possible for as long as possible,” said Linda Spilker, Voyager Project Scientist at NASA. The Jet Propulsion Laboratory in Southern California, which manages NASA’s mission.

Feed probes

Both Voyager probes are powered by radioisotope thermoelectric generators (RTGs), which convert heat from decaying plutonium into electricity. The continuous reduction process means that the generator produces slightly less electricity each year. So far, the reduction in power supply has not affected the scientific results of the mission, but to compensate for the loss, the engineers have turned off the heaters and other systems that are not necessary to keep the spacecraft in flight.

While Voyager 2 has run out of these options, it has become one of the five science instruments of the next spacecraft on the list. (Voyager 1 runs one less science instrument than its twin because one of the instruments failed early in the mission. As a result, the decision on whether to shut down the instrument on Voyager 1 won’t be made until next year.)

Looking for a way to avoid shutting down the Voyager 2 scientific instrument, the team took a closer look at the safety mechanism designed to protect the instruments in case of significant changes in the spacecraft’s voltage, electrical flow. Since voltage fluctuations can damage instruments, the Voyager is equipped with a voltage regulator that triggers a backup circuit in such a case. The circuit may draw a small amount of power from the RTG dedicated for this purpose. Instead of storing this power, the mission will now use it to keep the science tools up and running.

As a result, while the spacecraft’s voltage will not be tightly regulated, even after more than 45 years of flight, the electrical systems on both probes remain relatively stable, minimizing the need for a safety net. The engineering team can also monitor the voltage and react in case of excessive fluctuation. If the new approach works well on Voyager 2, the team could apply it to Voyager 1.

“Alternating voltage poses a risk to instruments, but we’ve determined that it’s a small risk and the alternative is a big reward because we can keep the science instruments on longer,” said Suzanne Dodd, Voyager project manager at JPL. “We’ve been observing the spacecraft for several weeks, and this new approach seems to be working.”

Voyager’s mission was originally intended to last only four years, and both probes were sent beyond Saturn and Jupiter. NASA expanded the mission to allow Voyager 2 to visit Neptune and Uranus; still the only spaceship to encounter ice giants. In 1990, NASA renewed the mission again, this time to send probes beyond the heliosphere. Voyager 1 reached the limit in 2012, and Voyager 2 (moving more slowly and in a different direction than its counterpart) reached the limit in 2018.