The Voyager 2 science mission has been extended for another 3 years

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Voyager 2: Spacecraft with large white parabolic antenna and long thin antennas. — Artistic concept of a Voyager spaceship in the darkness of space. The Voyagers are identical. NASA has devised a way for Voyager 2 to continue operating despite a dwindling power supply. This new plan will allow Voyager 2 to continue scientific operations for another 3 years instead of being shut down this year. Image via NASA/JPL-Caltech.

NASA published this original article on April 26, 2023. Adaptations from EarthSky.

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Extension of the science mission on Voyager 2

Launched in 1977, the Voyager 2 spacecraft is more than 12 billion miles (20 billion kilometers) from Earth and uses five scientific instruments to study interstellar space. In order to keep these instruments operating in the face of dwindling power supplies, the aging spacecraft has begun using a small reserve power bank designed as part of an onboard safety mechanism. The move will allow the mission to delay the shutdown of a scientific instrument to 2026, rather than this year.

Voyager 2 and its twin, Voyager 1, are the only spacecraft to ever operate outside of the heliosphere. The heliosphere is the sun’s protective bubble of particles and magnetic fields. The probes are helping scientists answer questions about the shape of the heliosphere and its role in protecting Earth from energetic particles and other radiation in the interstellar environment.

Linda Spilker, Voyager project scientist at NASA’s Jet Propulsion Laboratory in Southern California, who is leading the mission for NASA, said:

The scientific data that Voyager sends back becomes more valuable the farther away it travels from the sun, so we’re definitely interested in keeping as many scientific instruments running as long as possible.

Maintain power aboard Voyager 2

Both Voyager spacecraft are self-powered with radioisotope thermoelectric generators (RTGs). RTGs convert heat from decaying plutonium into electricity. Due to the continuous decay process, the generator produces slightly less electricity every year. So far, the sinking power supply has not affected the mission’s scientific performance. But to make up for the loss, engineers turned off heaters and other systems not strictly necessary to keep the spacecraft flying.

With those options now exhausted on Voyager 2, one of the spacecraft’s five scientific instruments was next on their list. (Voyager 1 operates one less scientific instrument than its twin because one instrument failed early in the mission. Therefore, the decision on whether to shut down an instrument on Voyager 1 will not be made until sometime next year.)

Looking for a way to avoid shutting down a Voyager 2 science instrument, the team took a closer look at a safety mechanism. They designed the safety mechanism to protect the instruments in case the spacecraft’s voltage — the current flow — changes significantly. Since a voltage fluctuation could damage the instruments, Voyager is equipped with a voltage regulator that activates a backup circuit in such a case. The circuit can access a small amount of power from the RTG dedicated for this purpose. Instead of reserving this energy, the mission will now use it to keep the scientific instruments running.

Metal canister with screws and wires. — Each of NASA’s Voyager spacecraft is equipped with 3 radioisotope thermoelectric generators (RTGs), including the one shown here. The RTGs power the spacecraft by converting the heat generated by the decay of plutonium-238 into electricity. Image via NASA/JPL-Caltech.

Keeping the science going

Although this does not tightly regulate the spacecraft’s voltage, the electrical systems on both probes remain relatively stable after more than 45 years in flight, minimizing the need for a safety net. The engineering team is also able to monitor the voltage and react if it fluctuates too much. If the new approach works well for Voyager 2, the team can implement it on Voyager 1 as well.

Suzanne Dodd, Voyager Project Manager at JPL said:

Variable voltages pose a risk to the instruments, but we have found the risk to be low and the alternative offers great reward as the scientific instruments can stay on for longer. We’ve been monitoring the spacecraft for a few weeks and it seems this new approach is working.

The lifespan of the Voyager missions

The Voyager mission was originally intended to last only four years and send both probes past Saturn and Jupiter. NASA extended the mission so Voyager 2 could visit Neptune and Uranus. It is still the only spaceship that has encountered these ice giants. In 1990, NASA extended the mission again, this time with the goal of sending the probes out of the heliosphere. Voyager 1 reached the boundary in 2012, while Voyager 2 (moving slower and in a different direction than its twin) reached it in 2018.

Conclusion: NASA found a way to conserve power on Voyager 2, allowing its scientific mission to be extended by another three years.

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