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

According to the plan, Voyager 2’s scientific instruments will be turned on a few years longer than previously planned, allowing for even more discoveries from interstellar space.

Voyager 2, launched in 1977, is more than 12 billion miles (20 billion kilometers) from Earth, using five science instruments to explore interstellar space. To help keep those instruments running despite the dwindling power supply, the aging spacecraft has begun using a small reservoir of backup power, set aside as part of the on-board safety mechanism. The move will allow the mission to delay shutting down the science instrument until 2026 instead of this year.

Voyager 2 and its twin, Voyager 1, are the only spacecraft ever to operate outside the heliosphere, the protective bubble of particles and magnetic fields produced by the Sun. The probes help 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 Voyagers bring back becomes more valuable the further they get away from the Sun, so we certainly have an interest in keeping as many science instruments as possible for as long as possible,” said Linda Spilker, Voyager project scientist at NASA’s Jet Propulsion Laboratory. A laboratory in Southern California that manages NASA’s mission.

Power 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 loss of power has not affected the mission’s science performance, but to compensate for the loss, engineers have turned off heaters and other systems that are not essential for the spacecraft to fly.

With those options now exhausted on Voyager 2, one of the spacecraft’s five science instruments was next on their list. (Voyager 1 has one less science instrument operating than its twin because the instrument failed early in the mission. So the decision to shut down the Voyager 1 instrument won’t be made until next year.)

Looking for a way to avoid shutting down Voyager 2’s science instrument, the team took a closer look at a safety mechanism designed to protect the instruments if the spacecraft’s voltage — the flow of electricity — changes significantly. Because voltage fluctuations can damage 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 that is reserved for this purpose. Instead of reserving this 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 of both probes remain relatively stable, 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 on 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 this is a low risk and the alternative offers a large reward because the science instruments can be turned on for longer,” said Susan Dodd, Voyager project manager at JPL. . “We’ve been observing the spacecraft for a few weeks, and this new approach seems to be working.”

Voyager’s mission was originally planned to last just four years, sending both probes past Saturn and Jupiter. NASA extended the mission so Voyager 2 could visit Neptune and Uranus; it remains the only spacecraft ever to encounter the ice giants. In 1990, NASA extended the mission again, this time with the goal of sending probes outside the heliosphere. Voyager 1 reached the limit in 2012, while Voyager 2 (moving slower and in a different direction than its twin) reached it in 2018.