The plan will keep Voyager 2’s science instruments running for a few years longer than previously expected, enabling more discoveries from interstellar space.
Launched in 1977, the Voyager 2 spacecraft is more than 12 billion miles (20 billion kilometers) from Earth, using five scientific instruments to study interstellar space. To help keep these instruments running despite dwindling power supplies, the aging spacecraft began using a small reservoir of backup power set aside as part of an onboard safety mechanism. The move would enable the mission to delay closing a science instrument until 2026, instead of this year.
Voyager 2 and its twin, Voyager 1, are the only two spacecraft to operate outside the heliosphere, the protective bubble of particles and magnetic fields generated by the sun. The probes help scientists answer questions about the heliosphere’s shape and role in protecting Earth from energetic particles and other radiation in the interstellar environment.
said Linda Spilker, Voyager project scientist at NASA’s Jet Propulsion Laboratory in Southern California, which manages the mission for NASA.
force for the probes
Both Voyager probes power themselves with radioisotope thermoelectric generators (RTGs), which convert heat from decaying plutonium into electricity. The continuous decay process means that the generator produces slightly less energy each year. So far, the low power supply hasn’t affected the mission’s science output, but to make up for the loss, engineers have turned off heaters and other systems that aren’t essential to keeping the spacecraft aloft.
With those options now exhausted on Voyager 2, one of the spacecraft’s five science instruments was next on their list. (Voyager 1 is operating a smaller science instrument than its twin due to an instrument failure at the start of the mission. As a result, a decision about turning off an instrument on Voyager 1 will not be made until sometime next year.)
Looking for a way to avoid shutting down a science instrument on Voyager 2, the team took a closer look at a safety mechanism designed to protect the instruments should the spacecraft’s voltage — the flow of electricity — change dramatically. Since fluctuations in voltage can damage instruments, Voyager is equipped with a voltage regulator that triggers a backup circuit in such an event. The circuit can access a small amount of power from the RTG intended for this. Instead of maintaining that power, the mission will now use it to keep science instruments running.
Although the spacecraft’s electrical voltage will not be tightly regulated as a result, even after more than 45 years in flight, the electrical systems on both probes remain relatively stable, reducing the need for a safety net. The engineering team is also able to monitor the voltage and respond if it fluctuates too much. If the new method works well for Voyager 2, the team may apply it to Voyager 1 as well.
said Susan Dodd, Voyager Project Manager at JPL. “We’ve been monitoring the spacecraft for a few weeks, and this new approach seems to be working.”
The Voyager mission was originally planned to last only four years, sending both probes past Saturn and Jupiter. NASA extended the mission so that Voyager 2 could visit Neptune and Uranus; It remains the only spacecraft to ever encounter ice giants. In 1990, NASA extended the mission again, this time with the goal of sending the probes outside the heliosphere. Voyager 1 reached the limit in 2012, while Voyager 2 (traveling slower and in a different direction than its twin) reached in 2018.