After a 44-year sojourn, travelling farther from Earth than any man-made object before, the Voyager spacecraft are entering their endgame. NASA has started turning off the probes’ systems that will make them completely defunct in a few years. Both the Voyager probes were launched in 1977 from Cape Canaveral — Voyager 2 actually took off first. The two identical probes travelled to the edge of the solar system and gave humanity the closest look at the moons of Saturn and Jupiter.
The probes were designed to last five years but have remarkably outlived that timeline and are still functioning despite going beyond the hot plasma bubble — the heliopause, which defines the beginning of the edge of the solar system.
NASA physicist Ralph McNutt told the Scientific American about powering down the probes: “We’re at 44 and a half years, so we’ve done 10 times the warranty…”
The probes are powered by radioisotope thermoelectric generators — powered by heat from decaying plutonium spheres — although the output is decreasing by about four watts a year. As of now, Voyager 1 has four functioning instruments left, while Voyager 2 has five.
“Because of the continual decline in the amount of power that is available, it is necessary to periodically reduce power consumption in order to maintain an adequate power margin,” NASA said.
It is certain that the plutonium powering the spacecraft will completely decay at some point. Some estimate it could be in 2025.
But the probes have surprised NASA engineers, who had expected to start turning off instruments on Voyager 2 from 2020. Instead, no instrument has been switched off since 2008.
“If everything goes really well, maybe we can get the missions extended into the 2030s. It just depends on the power. That’s the limiting point,” said Linda Spilker, who began working on the missions before they launched, told the Scientific American.
The two probes have travelled 14.46 billion kilometres, becoming the first man-made object to reach interstellar space. Voyager 1 breached the heliopause in 36 years, sending back data that suggests fascinating qualities about the role of magnetic fields in the universe. Voyager 2 passed into interstellar space in 2018 — 41 years after its launch.
At present, Voyager 1 is 14.5 billion miles (23.3 billion km) from Earth — it will take 20 light hours and 33 minutes to cover that distance. Voyager 2 is only 12 billion miles away, just under an 18-hour light distance.
