Voyager 1 Ghosts NASA, Forcing Use of Backup Radio Dormant Since 1981

Voyager 1 can’t seem to catch a break. The interstellar traveler recently recovered from a thruster glitch that nearly ended its mission, and now NASA’s aging probe stopped sending data to ground control due to an unknown issue.

On Monday, NASA revealed that Voyager 1 recently experienced a brief pause in communication after turning off one of its radio transmitters. The space agency is now relying on a second radio transmitter that hasn’t been used since 1981 to communicate with Voyager 1 until engineers can figure out the underlying issue behind the glitch.

The flight team behind the mission first realized something was amiss with Voyager 1’s communication when the spacecraft failed to respond to a command. On October 16, the team used NASA’s Deep Space Network (DSN)—a global array of giant radio antennas—to beam instructions to Voyager 1, directing it to turn on one of its heaters.

Voyager 1 should’ve sent back engineering data for the team to determine how the spacecraft responded to the command. This process normally takes a couple of days, as the command takes about 23 hours to travel more than 15 billion miles (24 billion kilometers) to the spacecraft and another 23 hours for the flight team to receive a signal back. Instead, the command seems to have triggered the spacecraft’s fault protection system, which autonomously responds to onboard issues affecting the mission.

The spacecraft’s fault protection system lowered the rate at which its radio transmitter was sending back data to use less power, according to NASA. However, while conserving the spacecraft’s power, this mode also changes the X-band radio signal, a frequency range within the electromagnetic spectrum that the DSN’s antennas listen for.

The flight team was able to locate the signal a day later but then, on October 19, communication with Voyager 1 stopped entirely. Voyager 1’s fault protection system appeared to have been triggered twice more, and it turned off the X-band transmitter altogether. The spacecraft switched to a second radio transmitter called the S-band, which uses less power but transmits a significantly fainter signal. Voyager 1’s S-band transmitter hadn’t been used since 1981, and the flight team was not sure its signal could be detected due to the spacecraft being much farther away today than it was 43 years ago.

Still, the team of engineers didn’t want to risk sending another signal to the X-band transmitter, and decided to give it a shot. On October 22, the team sent a command to confirm whether the S-band transmitter is working and was finally able to reconnect with Voyager 1 two days later. NASA engineers are currently working to determine what may have triggered the spacecraft’s fault protection system in its attempt to resolve the issue.

Voyager 1 launched in 1977, less than a month after its twin probe, Voyager 2, began its journey to space. The spacecraft took a faster route, exiting the asteroid belt earlier than its twin and making close encounters with Jupiter and Saturn. Along the way, it discovered two Jovian moons, Thebe and Metis, as well as five new moons and a new ring called the G-ring around Saturn. Voyager 1 ventured into interstellar space in August 2012, becoming the first spacecraft to cross the boundary of our solar system.

The spacecraft has been flying for 47 years, and all that time in deep space has taken a toll on the interstellar probe. NASA engineers have had to come up with creative ways to keep the iconic mission alive. The team recently switched to a different set of thrusters than the one the spacecraft had been relying on, which became clogged with silicon dioxide over the years, using a delicate procedure to preserve Voyager 1’s power. Earlier this year, the team of engineers also fixed a communication glitch that had been causing Voyager 1 to transmit gibberish to ground control.

Voyager 1 is no spring chicken, and its upkeep has not been an easy task over the years, especially from billions of miles away. But all-in-all, humanity’s long-standing interstellar probe is well worth the effort.