US space agency Nasa this week is trying to re-establish communications with the Voyager 1 spacecraft after it stopped sending understandable messages.
A post by the Jet Propulsion Laboratory, which runs the Voyager programme of two robotic interstellar probes, said that there was an issue where Voyager 1 is "receiving and executing commands sent from Earth" but a flight-data system computer on the spacecraft is not communicating properly in return.
It usually collects and transmits data back to Earth through the flight-data system, but it has not been able to successfully send "useable" data to engineers at Nasa.
"As a result, no science or engineering data is being sent back to Earth," the Laboratory's Calla Cofield wrote.
Voyager 1 is 24 billion kilometres away from Earth, the farthest spacecraft from home.
The two Voyager craft, since being launched in 1977, are known to be the longest-operating spacecraft.
A social media account for the Voyager spacecraft said: "Voyager 1 is having a bit of trouble with its Flight Data System, but our team is on it."
Nasa says it could take engineers weeks to "develop a new plan to remedy the issue", Ms Cofield wrote in the post.
It poses a unique challenge to rectify the problem because the computers on the spacecraft are decades old, and it takes nearly two days to see if a fix is successful.
