On February 25, mission engineers at NASA's Jet Propulsion Laboratory (JPL) in Southern California powered down the cosmic ray subsystem aboard Voyager 1, and on March 24, they will deactivate Voyager 2's low-energy charged particle instrument. Each spacecraft will retain three operational science instruments as part of an ongoing effort to extend their lifespan.
Launched in 1977, the Voyager probes rely on a radioisotope thermoelectric generator, which gradually loses power at a rate of approximately 4 watts per year.
"The Voyagers have been remarkable explorers since launch, and we aim to continue their legacy as long as possible," said Suzanne Dodd, Voyager project manager at JPL. "But with power levels dwindling, shutting down an instrument on each spacecraft now allows us to avoid reaching a critical point where a mission termination would become inevitable."
Each Voyager carried ten instruments at launch, several of which were designed for planetary flybys and have since been deactivated. The remaining instruments have been crucial in studying the heliosphere-the vast bubble of solar wind that surrounds the solar system-and interstellar space beyond it. Voyager 1 passed this boundary in 2012, followed by Voyager 2 in 2018, making them the only human-made objects to do so.
Last October, the plasma science instrument aboard Voyager 2 was turned off to conserve power. It had been operating with limited effectiveness due to its orientation relative to interstellar plasma flow. Voyager 1's plasma instrument had been shut down years earlier due to performance degradation.
Voyager 2's low-energy charged particle instrument, scheduled for shutdown later this month, has measured ions, electrons, and cosmic rays from the solar system and interstellar space. This instrument includes two subsystems: a particle telescope that captures broad energy ranges and a magnetospheric analyzer designed for focused studies. A rotating platform allows for 360-degree data collection, powered by a stepper motor that has vastly exceeded its original operational expectations. By the time of its deactivation, the motor will have completed more than 8.5 million steps.
"The Voyager spacecraft far exceeded their original planetary mission," said Patrick Koehn, Voyager program scientist at NASA Headquarters in Washington. "Every additional data point they collect is a scientific bonus and a testament to their extraordinary engineering, which has endured for nearly five decades."
For the time being, Voyager 1 will maintain operations of its magnetometer and plasma wave subsystem, while its low-energy charged particle instrument will remain active through 2025 before being powered down next year. Voyager 2 will continue running its magnetic field and plasma wave instruments, with its cosmic ray subsystem planned for shutdown in 2026.
These power-saving measures are expected to allow the spacecraft to continue functioning with at least one active science instrument into the 2030s. However, the durability of the nearly 50-year-old spacecraft remains uncertain, and unforeseen technical issues could shorten this timeline.
"Every moment the Voyagers continue to operate, they are exploring uncharted territory," said Linda Spilker, Voyager project scientist at JPL. "Each day could be the last, but each new day also brings the possibility of another groundbreaking discovery. We are doing everything we can to extend their pioneering mission for as long as possible."
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Voyager at ESA
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