Voyager 1 and 2 continue to make history every day, as they transmit data back to Earth while traveling further into deep space. But there will come a time when amassing distance is all they are capable of accomplishing. At some point, the batteries aboard each 47-year-old spacecraft will finally die, rendering the scientific probes into interstellar monuments to themselves.
However, NASA isn’t ready to say goodbye just yet, and is taking measures to get as much life out of the pair as possible. On March 5, Voyager mission engineers at the Jet Propulsion Laboratory in southern California confirmed they have already turned off Voyager 1’s cosmic ray subsystem experiment. NASA plans to do the same for Voyager 2’s low-energy charged particle instrument on March 24. Voyager project manager Suzanne Dodd explained cutting each program is a matter of life-or-death for both machines.
“Electrical power is running low,” Dodd said in a statement. “If we don’t turn off an instrument on each Voyager now, they would probably have only a few more months of power before we would need to declare ‘end of mission.’”
Launched in 1977, both Voyagers include an identical array of 10 instruments designed to gather a host of unprecedented cosmic information. Each probe is powered by three radioisotope thermoelectric generators (RTGs) fueled by decaying plutonium-238. The RTG arrays offered Voyager 1 and 2 about 470 watts at 30 volts when they first launched. Given the plutonium’s 87.74-year half-life, they now operate on about two-thirds their original power.
NASA has since turned off the majority of each spacecraft’s tools—some after completing the planetary fly-bys during the 1980s, and others as recently as October 2024. Voyager 1’s recent deactivation, for example, ended its decades’ long studies of cosmic radiation. For years, the cosmic ray subsystem’s three-telescope array observed fluctuations from protons and other deep space energies, and was integral in determining when and where Voyager 1 exited the heliosphere.
Voyager 2’s impending power-saving solution concerns its low-energy charged particle instrument that was designed to measure ions, electrons, and other cosmic forces. Both the cosmic ray subsystem and low-energy charged particle instrument rely on a 360-degree rotational platform powered by a 15.7-watt pulse motor every 192 seconds. Although the motor was originally tested to 500,000 steps (enough to make sure it lasted until Voyager 2 reached Saturn in August 1980), the motor will have since completed over 8.5 million steps at the time of its shut-off on March 24.
Despite recent technical difficulties and diminishing energy reserves, Voyager 1 and 2 aren’t down for the count just yet. Mission engineers plan to continue overseeing Voyager 1’s own low-energy charged particle instrument, as well as its magnetometer and plasma wave subsystem. Voyager 2’s magnetic field and plasma wave equipment will also continue operating for the foreseeable future, while its cosmic ray subsystem will be retired in 2026. If all goes according to plan, both spacecraft will continue sending back data from at least one instrument until some time in the 2030s.
“The Voyagers have been deep space rock stars since launch, and we want to keep it that way as long as possible,” Dodd said.
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