But not yet. This summer, engineers instructed Voyager 2 to fire up a set of thrusters that the spacecraft hasn’t used since 1989. Thrusters help keep the spacecraft steady, and the ones Voyager 2 was using were deteriorating, which meant they had to fire more often, until the number of pulses became “untenable,” according to NASA. Without healthy thrusters, the spacecraft would lose its ability to keep its antenna pointed toward Earth, the point of communication between the spacecraft and its stewards back home. Voyager 1 made the same switch last year.

Read: When will Voyager stop calling home?

Engineers also shut off a heating component that keeps one of Voyager 2’s instruments warm enough to function in the frigid cold of space. Turning off a heater buys the mission four watts, the same amount it loses in a year. After months of deliberation, scientists decided that sacrificing this instrument, which last year helped confirm that the spacecraft had entered the space between stars, was worth it. Unlike the others, this instrument can point only in certain directions.

Some other instruments have, incredibly, tolerated the loss of their heaters, sometimes for years. According to NASA, the temperature of the cosmic-ray instrument, the most recent target of rationing, has dropped to –74 degrees Fahrenheit (–59 degrees Celsius), far lower than what it withstood during testing on Earth. But it’s still collecting data and beaming them home.

Heaters on instruments on both Voyagers will be next on the chopping block. Suzanne Dodd, the Voyager project manager at NASA’s Jet Propulsion Laboratory, says the team may someday be forced to turn off one of the engineering elements that help the spacecraft communicate with Earth. “If it does work, then we gain two more watts,” Dodd says. “If it doesn’t work, then we lose the mission.”

No one was thinking about interstellar space when the Voyager spacecraft were dispatched. Scientists and engineers had set their sights much closer to home: the other planets, arranged in a rare alignment that allowed the spacecraft to swing from one to the next. “The twin Voyagers, despite all the odds to the contrary, have been our accidental visitors to the beginning of the space between the stars themselves,” says Ralph McNutt, a scientist at Johns Hopkins Applied Physics Laboratory who still works on the mission.

Read: Voyager made the solar system a real place

Both spacecraft reached Jupiter first, capturing the planet’s swirling filigree of storms in unprecedented detail. Voyager 1 bopped from there to Saturn. Scientists were particularly interested in the planet’s largest moon, Titan, which would turn out to be one of the most intriguing spots in the solar system and a potential home of extraterrestrial life. If Voyager 1 didn’t collect enough good data before moving on, Voyager 2 would be redirected to try again. But the flyby worked, allowing Voyager 2 to swoop past Saturn and on to Uranus and Neptune.