"It's not every day that you get to update the firmware on a device that was produced in the 1970s," writes Hackaday, "and rarely is said device well beyond the boundaries of our solar system.

"This is however exactly what the JPL team in charge of the Voyager 1 & 2 missions are facing, as they are in the process of sending fresh firmware patches over to these amazing feats of engineering."

From NASA's announcement: One effort addresses fuel residue that seems to be accumulating inside narrow tubes in some of the thrusters on the spacecraft. The thrusters are used to keep each spacecraft's antenna pointed at Earth. This type of buildup has been observed in a handful of other spacecraft... In some of the propellant inlet tubes, the buildup is becoming significant. To slow that buildup, the mission has begun letting the two spacecraft rotate slightly farther in each direction [almost 1 degree] before firing the thrusters. This will reduce the frequency of thruster firings... While more rotating by the spacecraft could mean bits of science data are occasionally lost — akin to being on a phone call where the person on the other end cuts out occasionally — the team concluded the plan will enable the Voyagers to return more data over time.

Engineers can't know for sure when the thruster propellant inlet tubes will become completely clogged, but they expect that with these precautions, that won't happen for at least five more years, possibly much longer. "This far into the mission, the engineering team is being faced with a lot of challenges for which we just don't have a playbook," said Linda Spilker, project scientist for the mission as NASA's Jet Propulsion Laboratory in Southern California. "But they continue to come up with creative solutions."

But that's not the only issue: The team is also uploading a software patch to prevent the recurrence of a glitch that arose on Voyager 1 last year. Engineers resolved the glitch, and the patch is intended to prevent the issue from occurring again in Voyager 1 or arising in its twin, Voyager 2...

In 2022, the onboard computer that orients the Voyager 1 spacecraft with Earth began to send back garbled status reports, despite otherwise continuing to operate normally... The attitude articulation and control system (AACS) was misdirecting commands, writing them into the computer memory instead of carrying them out. One of those missed commands wound up garbling the AACS status report before it could reach engineers on the ground.

The team determined the AACS had entered into an incorrect mode; however, they couldn't determine the cause and thus aren't sure if the issue could arise again. The software patch should prevent that.

"This patch is like an insurance policy that will protect us in the future and help us keep these probes going as long as possible," said JPL's Suzanne Dodd, Voyager project manager. "These are the only spacecraft to ever operate in interstellar space, so the data they're sending back is uniquely valuable to our understanding of our local universe."

Since their launch in 1977, NASA's two Voyager probes have travelled more than 12 billion miles (each!), and are still sending back data from beyond our solar system.