Voyager 1: Remote heating repair ensures continued operation

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Employees at NASA's Jet Propulsion Laboratory (JPL) in southern California have successfully repaired a heating system under difficult conditions. From a distance of 25 billion kilometers, they successfully put the engines of the Voyager 1 space probe back into operation. These had actually been considered irreparable since 2004 and were abandoned. However, because the reserve engines used since then were also in danger of failing and, on top of that, the connection to the probe was restricted for several months, a new test was carried out, and a solution was found, as JPL has now announced.

The engines and their reserve systems, which have now been put back into operation, are needed to align the probe so that its antennas point towards Earth. Only in this way can data be transmitted from it and, conversely, control commands be sent to it. The roll thrusters rotate the probe around its longitudinal axis, with a guide star serving as orientation. There is also another group of thrusters for course changes, which was used for flybys of the outer planets in the solar system. This was also reactivated in 2018/2019, but cannot be used for roll movements.

Incorrectly set switch

The primary roll thrusters were originally abandoned in 2004 after the internal heaters stopped working. After a thorough inspection, these were deemed irreparable. From today's perspective, this was a rash decision, but it was obviously made because the backup systems were perfectly adequate and nobody at NASA expected the spacecraft to last that long 20 years ago.

Now, however, the fuel lines of the backup thrusters were becoming increasingly clogged and failure was imminent. NASA engineers therefore checked the primary systems once again and came to the conclusion that perhaps only one switch was in the wrong position due to a circuit fault. It was hoped that this could be moved back into the correct position by remote control. The maneuver was not without risk. In the worst-case scenario, an explosion could have occurred. This could have destroyed Voyager or at least rendered it unable to maneuver.

23 hours signal transit time

Fortunately, this was not the case when the commands were sent to the probe on March 20. Within 20 minutes, a rise in temperature was detected in the engine heaters. However, due to the signal propagation time, the engineers on Earth were only able to receive the feedback after 23 hours – this is how long it takes for the signal to travel from the probe to Earth and vice versa.

A planned outage at Deep Space Station 43 (DSS-43) in Canberra, Australia, created additional time pressure. The antenna with a diameter of 70 meters is the only one in NASA's globally distributed Deep Space Network that has sufficient signal strength to reach the Voyager probes. As the facility, which was built in the 1970s, is to be made fit for planned new NASA missions, it will be largely unavailable between May 2025 and February 2026, except for short operating windows. As a result, the repairs to Voyager 1 had to be completed by then to avoid the risk of the probe's backup engines failing in the meantime and the probe no longer being accessible.

Traveling in interstellar space

Voyager 1 and its sister probe Voyager 2 set off on their missions to explore the solar system in 1977. They are now traveling at 56,000 km/h in interstellar space and are still functional despite some limitations. Voyager 1 is currently around 25 billion kilometers from Earth, Voyager 2 around 21 billion kilometers. This is not the first spectacular remote maintenance on Voyager 1: NASA already managed to find a solution to a memory defect that had caused faulty transmissions in 2024.

(mki)