NASA is shutting down two science instruments on its Voyager spacecraft to conserve power and extend their missions.

Voyager 2 will turn off an instrument measuring charged particles and cosmic rays later this month, while Voyager 1 powered down a similar instrument last week.

The spacecraft, launched in 1977, are now in interstellar space, with Voyager 1 over 15 billion miles from Earth and Voyager 2 over 13 billion miles away, the Associated press has reported.

Despite the shutdowns, both spacecraft still have three active instruments to study the sun’s protective bubble and the space beyond.

Written by B.C. Begley