The software patch will be received from over 19 billion kilometres away in a bid to keep the spacecraft operational.
Voyager 1 was first launched in 1977 on a path that eventually led both it and its sister spacecraft, Voyager 2, outside the solar system altogether.
But in recent years, Nasa said that fuel residue has been accumulating inside narrow tubes in some of the thrusters on both spacecraft. Voyager 1 has also faced problems with sending junk data back home after it suddenly began routing its telemetry data through a derelict onboard computer for unknown reasons.
The thrusters on Voyager 1 and Voyager 2 are primarily used to keep the spacecraft antennae pointed at Earth in order to communicate. As spacecraft can rotate in three directions, Voyager’s thrusters automatically fire to reorient itself.
Each time a thruster fires, it adds tiny amounts of propellant residue, leading to gradual build-up of material over decades. To slow that build-up, the mission has begun letting the two spacecraft rotate slightly farther in each direction before firing the thrusters.
The adjustments to the thruster rotation range were made by commands sent in September and October, and they allow the spacecraft to move almost one degree further in each direction than in the past.
While more rotating by the spacecraft could mean bits of science data are occasionally lost, the team believes the plan will enable the Voyagers to return more data in the long run.
“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. “But they continue to come up with creative solutions.”
In 2022, the onboard computer that orients Voyager 1 with Earth began to send back garbled status reports, despite otherwise operating normally. Mission engineers eventually realised that 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.
“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 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.”
Voyager 1 and Voyager 2 have travelled more than 15 billion and 12 billion miles (24 billion and 19 billion kilometres) from Earth, respectively. At those distances, the patch instructions will take over 18 hours to travel to the spacecraft.
Because of their age and the communication lag time, there’s some risk the patch could overwrite essential code or have other unintended effects on the spacecraft. To reduce those risks, the team has spent months writing, reviewing and checking the code.
