NASA’s Voyager will do more science with a new power strategy

The plan will keep Voyager 2’s science instruments going for a few years longer than previously expected, enabling even 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 science instruments to study interstellar space. To help keep those instruments operating despite dwindling power supplies, aging spacecraft have begun using a small reservoir of backup power as part of an onboard safety mechanism. The move will help the mission postpone the shutdown of the science instrument until 2026, rather than this year.

Voyager 2 and its twin Voyager 1 are the only spacecraft to date to operate outside the heliosphere, the protective bubble of particles and magnetic fields produced 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 from the interstellar atmosphere.

“The science data the Voyagers are returning becomes more valuable the farther they get from the Sun, so we’re certainly interested in keeping the science instruments operational for as long as possible,” said Linda Spilker, Voyager project scientist at NASA’s Jet Propulsion. ” Laboratory in Southern California, which manages missions for NASA.

Power the probes

Both Voyager probes are powered by radioisotope thermoelectric generators (RTGs), which convert heat from decaying plutonium into electricity. A continuous decay process means that the generator produces slightly less power each year. So far, the reduced power supply has not affected the mission’s science output, but to compensate for the loss, engineers have turned off heaters and other systems not needed to keep the spacecraft flying.

With Voyager 2 now running out of those options, one of the spacecraft’s five science instruments was next on their list. (Voyager 1 is running one less science instrument than its twin because one instrument failed early in the mission. As a result, a decision on whether to shut down any instruments on Voyager 1 will not come until sometime next year.)

Looking for a way to avoid shutting down the 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 current of electricity — changes significantly. Because voltage fluctuations can damage equipment, 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 set aside for this purpose. Instead of reserving that power, the mission will now use it to keep science instruments running.

Although the spacecraft’s voltage will not be tightly regulated as a result, even after more than 45 years of flight, the electrical systems on both probes remain relatively stable, reducing the need for safety nets. 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 voltage poses a risk to the instruments, but we’ve determined that it’s a small risk, and the alternative offers a large reward of being able to keep the science instruments running for longer,” said Suzanne Dodd, Voyager’s project manager at JPL. . “We’ve been observing the spacecraft for a few weeks now, and it looks like this new approach is working.”

The Voyager mission was originally intended to last only four years, examining both the planets Saturn and Jupiter. NASA extended the mission so Voyager 2 could visit Neptune and Uranus; It is still the only spacecraft to have encountered the ice giants. In 1990, NASA extended the mission again, this time with the goal of sending the probe beyond the heliosphere. Voyager 1 reached the boundary in 2012, while Voyager 2 (traveling slower and in a different direction than its twin) arrived in 2018.