A spacecraft can’t live among the stars forever.
But NASA isn’t quite ready to say goodbye to its 1970s-era Voyager 2, its second-farthest spacecraft exploring what lies beyond the solar system’s outermost planets. It is slowly dying as it hurtles through interstellar space at more than 34,000 mph.
Voyager’s team of engineers has already turned off heaters and other power vampires that aren’t crucial for flying. The situation has become more dire, though. With the spacecraft’s power supply dwindling, NASA was on the brink of shutting down one of its five onboard science instruments. That would mark the beginning of the end for the decades-long science mission.
In the nick of time, engineers devised a new plan to squeeze more life out of Voyager 2. From 12 billion miles away, they’ve pinpointed a hidden trove of power within one of its parts that could prevent them from having to shut down a key instrument for another three years.
“The science data that the Voyagers are returning gets more valuable the farther away from the sun they go, so we are definitely interested in keeping as many science instruments operating as long as possible,” said Linda Spilker, Voyager’s project scientist at NASA’s Jet Propulsion Laboratory, in a statement.
Both Voyager 2 and its twin, Voyager 1, are way older than their original life expectancy. They were intended to study Jupiter and Saturn, their moons, and Saturn’s rings. For the two-planet mission, they were built to last just five years.
After their initial success, engineers doubled the mission objectives to include two more planets: Uranus and Neptune. Together they’ve explored four planets, 48 moons, and a host of planetary magnetic fields and rings.
Now the Voyager spacecraft are exploring the limits of the sun’s influence. They are the first probes to travel outside the so-called “heliosphere,” the sun’s protective bubble of particles and magnetic fields. The twins are helping scientists answer questions about its role in shielding Earth from radiation found in the interstellar environment. Scientists define interstellar space as the place outside the sun’s constant flow of material affecting its surroundings.
Engineers found the extra stash of power in a part designed to protect the science instruments from changes in their voltage. Electrical fluctuations could potentially damage instruments, so a regulator triggers a backup circuit to access the reserved power from their generators. Now Voyager 2’s instruments will use the power rather than set it aside.
Both Voyager probes work on radioisotope thermoelectric generators, which turn heat from decaying plutonium into electricity. The process yields less power each year.
As far as Voyager 1 goes, it is already operating one fewer science instrument than its sibling because one of its instruments failed early in the mission. That means NASA won’t have to decide whether to turn another off until next year. If this new power strategy works for Voyager 2, the team will consider doing the same for Voyager 1.
Although Voyager 2 is now flying without a voltage safety net, engineers feel confident that its electricity is relatively stable, posing a small risk to the onboard instruments.
“The alternative offers a big reward of being able to keep the science instruments turned on longer,” said Suzanne Dodd, Voyager’s project manager, in a statement. “We’ve been monitoring the spacecraft for a few weeks, and it seems like this new approach is working.”