NASA specialists reported a unique repair operation. They were able to restart the Voyager 1 attitude control system’s thrusters, which had lost power back in 2004.
Clogging of Voyager 1’s thrusters
Voyager 1 was launched in 1977 and reached sufficient speed to leave the solar system forever. To maintain communication with Earth, the vehicle is equipped with a pair of sets of attitude system thrusters. Each day, they deliver a series of short pulses lasting tens of milliseconds that help keep Voyager 1’s antenna pointed at Earth and the star sensor pointed at the navigational star used to keep it properly oriented. Hydrazine is used as a fuel, which is converted into a gas and released in jets, correcting the position of the vehicle.
As early as the turn of the century, engineers noticed that some of the fuel tubes in the Voyager 1 attitude system thrusters were beginning to clog with silicon dioxide. It’s a byproduct that has separated with age from the rubber diaphragm in its fuel tank. As a result, mission specialists decided to alternate thrusters.
In 2004, Voyager 1’s main set of attitude control system thrusters stopped working after power was lost in two small internal heaters. Engineers decided that the broken heaters were likely beyond repair and decided to rely solely on the backup thrusters.
It was a good solution to the problem at the time. However, by their own admission, the engineers did not realize that Voyager 1 would operate for another 20 years. As a result, the fuel tubes in the backup thrusters of the attitude control system are also clogged. It is estimated that by the autumn of 2025 they may already stop working.
Repair in interstellar space
In this situation, mission specialists decided to repair the main set of orientation system thrusters, which had not worked since 2004. The plan was to turn on the thrusters and then restore the heaters and restart them. This was a risky operation because if the vehicle’s star sensor deviated too far from the navigational star during the repair, a program would be triggered that automatically started the thrusters. If the heaters were still out, it could have caused a small explosion.
An additional challenge was posed by the fact that the 70-meter antenna of NASA’s Long Range Space Communications Complex would undergo an upgrade from May 4, 2025 to February 2026. It is the only antenna on Earth with enough power to transmit commands to Voyager. Therefore, the repair operation had to be completed before it could be modernized.
The interstellar repair ended in success. On March 20, engineers received temperature rise data from the heaters showing that their operation had been restored. This means that the craft once again has a spare set of thrusters that it will be able to use to provide communications with Earth.
According to NASA
