This artist’s concept shows NASA’s Voyager spacecraft against a field of stars in the darkness of space. The two Voyager spacecraft are traveling farther and farther from Earth, on a journey into interstellar space, and will eventually orbit the center of the Milky Way. Credit: NASA/JPL-Caltech
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.
Turning off a scientific instrument will not finish the job. After shutting down one instrument in 2026, the probe will continue to power four science instruments until a low power supply requires the shutdown of another. If Voyager 2 remains healthy, the engineering team expects the mission to continue for years to come.
The Voyager proof test model, displayed in the space simulation room at JPL in 1976, was an exact replica of the twin Voyager space probes launched in 1977. The model’s surveying platform extends to the right, holding several of the spacecraft’s science instruments in publishing it. positions. Credit: NASA/JPL-Caltech
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[{” attribute=””>NASA’s Jet Propulsion Laboratory in Southern California, which manages the mission for NASA.
Power to the Probes
Both Voyager probes power themselves with radioisotope thermoelectric generators (RTGs), which convert heat from decaying plutonium into electricity. The continual decay process means the generator produces slightly less power each year. So far, the declining power supply hasn’t impacted the mission’s science output, but to compensate for the loss, engineers have turned off heaters and other systems that are not essential to keeping the spacecraft flying.
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 one less science instrument than its twin because an instrument failed early in the mission. As a result, the decision about whether to turn off an instrument on Voyager 1 won’t come until sometime next year.)
Each of NASA’s Voyager probes are equipped with three radioisotope thermoelectric generators (RTGs), including the one shown here. The RTGs provide power for the spacecraft by converting the heat generated by the decay of plutonium-238 into electricity. Credit: NASA/JPL-Caltech
In search of a way to avoid shutting down a Voyager 2 science instrument, the team took a closer look at a safety mechanism designed to protect the instruments in case the spacecraft’s voltage – the flow of electricity – changes significantly. Because a fluctuation in voltage could damage the 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 that’s set aside for this purpose. Instead of reserving that power, the mission will now be using it to keep the science instruments operating.
Although the spacecraft’s 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, minimizing 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 approach works well for Voyager 2, the team may implement it on Voyager 1 as well.
“Variable voltages pose a risk to the instruments, but we’ve determined that it’s a small risk, and the alternative offers a big reward of being able to keep the science instruments turned on longer,” said Suzanne Dodd, Voyager’s project manager at JPL. “We’ve been monitoring the spacecraft for a few weeks, and it seems like this new approach is working.”
The Voyager mission was originally scheduled 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 is still the only spacecraft ever to have encountered the 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 boundary in 2012, while Voyager 2 (traveling slower and in a different direction than its twin) reached it in 2018.
More About the Mission
Jet Propulsion Laboratory (JPL), a division of Caltech in Pasadena, built and operates the Voyager spacecraft. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington.