Spacecraft Voyager 1 and Voyager 2 have travelled to places in space where no other human-made objects have gone before, but their lives will end soon. The engineers at the US space agency, National Aeronautics and Space Administration (NASA), are turning off one instrument each on both spacecraft so that they continue with their job of space exploration. 

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The Voyager programme consists of two spacecraft, Voyager 1 and Voyager 2, launched in 1977 to study the outer Solar System and beyond. Currently, both are exploring uncharted territory in interstellar space. 

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Voyager 1 and Voyager 2 reached interstellar space in 2012 and 2018, respectively. The two spacecraft have travelled a combined 29 billion miles to become the farthest human-built objects from Earth. 

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The mission engineers at NASA's Jet Propulsion Laboratory (JPL) deactivated Voyager 1's cosmic ray subsystem experiment on February 25. They will shut down the low-energy charged particle instrument onboard Voyager 2 on March 24. 

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When they were launched weeks apart in 1977, the Voyager probes carried identical sets of 10 science instruments. The Voyager probes consist of a radioisotope power system and a nuclear battery that harnesses the heat of decaying plutonium to produce electricity. The system generated 470 watts of power at the time of launch, but as the plutonium degraded, that amount dropped. 

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Over time, the probes’ power supply has gradually diminished. The Voyager spacecraft rely on electricity generated from the heat of decaying plutonium, and both are losing an estimated 4 watts of power per year. 

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"The Voyagers have been deep space rock stars since launch, and we want to keep it that way as long as possible," said Suzanne Dodd, Voyager project manager at JPL, in a statement. 

"But electrical power is running low. 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," the statement added. 

NASA officials have already expressed the agency's intention to have both Voyager spacecraft still in service by 2027 when they celebrate their 50th anniversary. 

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The probes will be able to survive for another two years only by carefully controlling the dwindling power supply. Out of their 10 instruments, only three will be powered by the end of March due to recent cullings. By 2026, they will only have two instruments left. 

Linda Spilker, who is a Voyager project scientist at JPL, said, "Every minute of every day, the Voyagers explore a region where no spacecraft has gone before. That also means every day could be our last. But that day could also bring another interstellar revelation. So, we're pulling out all the stops, doing what we can to make sure Voyagers 1 and 2 continue their trailblazing for the maximum time possible." 

(With inputs from agencies)