NASA engineers accomplished an extraordinary feat in 2017 by successfully reactivating a set of Voyager 1 thrusters that had remained unused for 37 years, allowing the iconic spacecraft to continue communicating with Earth despite being more than 21 billion kilometers away in interstellar space.
The command was transmitted from NASA’s Jet Propulsion Laboratory on November 28, 2017, and took 19 hours and 35 minutes to reach Voyager 1. Engineers then waited another 19 hours for confirmation that the spacecraft had executed the instructions correctly. Telemetry revealed that the dormant thrusters fired a series of precise 10-millisecond pulses exactly as planned, restoring a backup system that had not been used since November 1980.
The revived thrusters were not used to propel Voyager through space. Instead, they performed tiny orientation adjustments that kept the spacecraft’s 3.7-meter high-gain antenna accurately pointed toward Earth. At Voyager’s immense distance, even a slight misalignment could cause the narrow radio beam to miss Earth entirely, cutting off communications.
NASA turned to the backup thrusters after the spacecraft’s primary attitude-control system began showing signs of degradation in 2014. The unused thrusters had originally been designed for trajectory correction maneuvers during Voyager’s flybys of Jupiter and Saturn and had never been used for routine attitude control.
Before sending the commands, engineers recovered decades-old technical documents and analyzed software written in an obsolete assembly language to predict how the dormant hardware would respond. Because of the nearly 40-hour communication delay, every step had to be carefully validated before transmission, leaving no opportunity for real-time intervention.
The successful test extended Voyager 1’s operational life by allowing engineers to switch to the backup thrusters in early 2018. Voyager 2 later underwent a similar transition in 2019.
Although the achievement demonstrated the remarkable durability of the spacecraft’s engineering, it did not stop the effects of aging. Voyager’s nuclear power source continues to lose electrical output each year, forcing NASA to gradually shut down scientific instruments to conserve energy. Nearly five decades after its 1977 launch, however, Voyager 1 continues to send valuable scientific data from interstellar space, thanks to both its robust design and the ingenuity of generations of engineers who continue to keep the historic mission alive.
