For more than 46 years, the Voyager 1 probe has been traveling through space. On August 25th, 2012, it became the first spacecraft to cross the heliopause and enter interstellar space. Since then, mission controllers have maintained contact with the probe as part of an extended mission, which will last until the probe’s radioisotopic thermoelectric generators (RTGs) finally run out. Unfortunately, the Voyager 1 probe has been showing its age and signs of wear and tear, which is unavoidable when you’re the farthest spacecraft from Earth.
This includes issues with some of the probe’s subsystems, which have been a bit buggy lately. For instance, engineers at NASA recently announced that they were working to resolve an error with the probe’s flight data system (FDS). This system consists of three onboard computers responsible for communicating with another of Voyager 1’s subsystems, known as the telemetry modulation unit (TMU). As a result, while the spacecraft can receive and execute commands sent from Earth, it cannot send any science or engineering data back.
The main purpose of the FDS is to collect data from the probe’s science instruments and engineering data from the spacecraft itself. This data is then combined into a single package and sent to the TMU, which transmits in binary code back to Earth. Recently, mission controllers noticed that the TMU was transmitting a repeating pattern of ones and zeroes, which raised some eyebrows. After reviewing and ruling out all other potential causes, the Voyager team determined that the FDS was the source of the problem.
Over the weekend, the mission team attempted to restart the FDS in the hopes that this would restore it to a working state. They did not succeed, and now the team anticipates that it could take several more weeks to develop a new plan to address the problem. This was not unexpected since both Voyager and its twin (Voyager 2) are the longest-serving spacecraft in history. When they launched in 1977, both probes represented cutting-edge astronautics, navigation, and communication technology.
However, both are now over forty years out of date, so finding solutions to problems often requires engineers and technical experts to consult the original documents. These decades-old documents were created by engineers who didn’t anticipate of problems the probes are countering today. As a result, it takes the mission team time to determine how a new command will affect the spacecraft’s operations and how to avoid unintended consequences. What’s more, commands from mission controllers take 22.5 hours to reach Voyager 1, which means that two-way communications take 45 hours.
This means that Voyager 1’s controllers have to wait almost two full days before they will learn if the solution they implemented worked. In the meantime, all NASA can do is troubleshoot the problem and wait for a solution that works to take effect. As for the Voyager 1 probe, it continues to explore the outermost regions of the Solar System and the is farthest artificial objects from Earth – 24 billion km (15 billion mi) and counting!
Further Reading: NASA