15 Billion Miles Away, NASA’s Voyager 1 Breaks Its Silence

NASA reconnected with Voyager 1 after a fault protection system prompted the spacecraft to turn off a transmitter.

Engineers at JPL are investigating the incident, facing the challenge of managing commands and data over a 15 billion-mile distance. The team aims to stabilize communications and address the technical difficulties of the aging spacecraft in interstellar space.

Reestablishing Contact With Voyager 1

On October 24, NASA successfully reestablished contact with the Voyager 1 spacecraft after a brief communication pause. Recently, Voyager 1 shut off one of its two radio transmitters, and NASA’s team is now working to identify the cause.

The shutdown appears to have been triggered by the spacecraft’s fault protection system, which automatically manages onboard issues. This system conserves power by disabling non-essential systems if the spacecraft’s power supply is overstretched. However, it could take days to weeks for the team to pinpoint what exactly activated the fault protection system.

Troubleshooting and Command Response

NASA’s Jet Propulsion Laboratory (JPL) in Southern California manages communications with Voyager 1 via the Deep Space Network. When the JPL team sends instructions, Voyager 1 responds by transmitting engineering data, which helps the team assess its reaction to the command. This back-and-forth takes around two days—nearly 23 hours for the command to travel over 15 billion miles (24 billion kilometers) to Voyager 1 and another 23 hours for the data to return to Earth.

On October 16, the flight team sent a command to turn on one of the spacecraft’s heaters. While Voyager 1 should have had ample power to operate the heater, the command triggered the fault protection system. The team learned of the issue when the Deep Space Network couldn’t detect Voyager 1’s signal on October 18.

Communication Challenges and Solutions

The spacecraft typically communicates with Earth using what’s called an X-band radio transmitter, named for the specific frequency it uses. The flight team correctly hypothesized that the fault protection system had lowered the rate at which the transmitter was sending back data. This mode requires less power from the spacecraft, but it also changes the X-band signal that the Deep Space Network needs to listen for. Engineers found the signal later that day, and Voyager 1 otherwise seemed to be in a stable state as the team began to investigate what had happened.

Then, on October 19, communication appeared to stop entirely. The flight team suspected that Voyager 1’s fault protection system was triggered twice more and that it turned off the X-band transmitter and switched to a second radio transmitter called the S-band. While the S-band uses less power, Voyager 1 had not used it to communicate with Earth since 1981. It uses a different frequency than the X-band transmitters signal is significantly fainter. The flight team was not certain the S-band could be detected at Earth due to the spacecraft’s distance, but engineers with the Deep Space Network were able to find it.

Mission Continuity and Challenges

Rather than risk turning the X-band back on before determining what triggered the fault protection system, the team sent a command on Oct. 22 to confirm the S-band transmitter is working. The team is now working to gather information that will help them figure out what happened and return Voyager 1 to normal operations.

Voyagers 1 and 2 have been flying for more than 47 years and are the only two spacecraft to operate in interstellar space. Their advanced age has meant an increase in the frequency and complexity of technical issues and new challenges for the mission engineering team.