Voyager 1, the most distant man-made object from Earth, shut down one of its three remaining instruments as NASA worked to extend its near-half-century mission.

The Voyager probes launched in 1977 toward the solar system’s outer planets, a planned five-year job. But they have continued to function in the decades since, slowly cutting down capabilities as their nuclear batteries dwindle.

They are now both in interstellar space. Voyager 1, the most distant, is 15.8 billion miles away, and radio signals from Earth take almost 24 hours to reach it. But space is big: If it were heading in the right direction, which it isn’t, Voyager 1 would take a further 70,000 years to reach our nearest stellar neighbor.