Voyager 1 Went Silent for Five Months in 2023. NASA Wasn't Sure It Was Coming Back.

Voyager 1 is 24 billion kilometres from Earth. It has been travelling for 47 years. It is moving at approximately 61,000 kilometres per hour and it is still accelerating, carried by the momentum of a gravity assist manoeuvre performed in 1980. It crossed into interstellar space in 2012 — the first human-made object to do so — and it is still transmitting. In November 2023, it started sending back nonsense.

The problem was traced to a single chip in the flight data system computer — one of three onboard computers that manage Voyager 1's operations. The chip, which stores a portion of the software responsible for packaging scientific and engineering data for transmission, had become corrupted. The spacecraft was still functioning. It simply could not communicate coherently. Every transmission was garbled.

The challenge facing NASA's Jet Propulsion Laboratory was considerable. Voyager 1's computers run on technology from the early 1970s. The original engineers who designed the systems are mostly retired or dead. The documentation is incomplete. And every command sent to the spacecraft takes 22.5 hours to arrive — meaning that any attempt to fix the problem required waiting 45 hours for a round-trip response, with no guarantee that the command had worked.

The team that worked on the fix included engineers who had been brought back out of retirement specifically because they were among the few people alive who understood the original architecture. The solution they devised was elegant: rather than attempting to repair the corrupted memory, they redistributed the affected code across other memory locations on the chip, working around the damaged section entirely. The commands to implement this had to be written in a programming language that has not been in common use since the 1970s.

In April 2024, after five months of silence, Voyager 1 began returning coherent data again. The fix had worked. The spacecraft resumed normal operations — transmitting readings from its plasma wave, magnetic field, and cosmic ray instruments, all of which continue to function after nearly five decades in space.

Voyager 1's power source — a radioisotope thermoelectric generator — is expected to provide enough electricity to keep at least some instruments running until approximately 2025. After that, the spacecraft will go dark. It will continue travelling outward through interstellar space for millions of years, carrying a gold-plated record containing sounds and images from Earth, addressed to whoever might eventually find it. The nearest star it will pass is AC+79 3888, in the constellation Camelopardalis. It will arrive in approximately 40,000 years.