Twin Voyager examines approaching 45th birthdays and difficult decisions

Twin Voyager examines approaching 45th birthdays and difficult decisions

On August 20, 1977, NASA’s Voyager 2 spacecraft was launched into space. Its twin, Voyager 1, was launched 16 days later. Today, they are not only the most distant man-made objects – 12 billion and 14.5 billion miles (19.3 billion and 23.3 billion kilometers) from Earth, respectively – but also NASA’s longest-operating mission, which continues to send back data from their interstellar journey towards the edge of the solar system as they approach their 45th anniversary.

But each Voyager spacecraft powered by a finite nuclear energy source, and both sources are declining to dangerously low levels. Each spacecraft has a stockpile of the radioactive isotope plutonium-238; when the isotope decays, it releases energy that is converted into electricity by three radioisotope thermoelectric generators (RTGs). At launch, the RTGs provided each spacecraft with 450 watts of power. Now they produce less than half that amount, and their electrical output declines by four watts each year.

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