NASA is switching off two science instruments on its long-running twin Voyager spacecraft to save power.
The space agency said on Wednesday an instrument on Voyager 2 that measures charged particles and cosmic rays will shut off later in March.
Last week, NASA powered down an instrument on Voyager 1 designed to study cosmic rays.
The energy-saving moves were necessary to extend their missions, Voyager project manager Suzanne Dodd at the NASA Jet Propulsion Laboratory said in a statement.
The twin spacecraft launched in 1977 and are currently in interstellar space, or the space between stars.
Voyager 1 discovered a thin ring around Jupiter and several of Saturn's moons, and Voyager 2 is the only spacecraft to visit Uranus and Neptune.
Each spacecraft still has three instruments apiece to study the sun's protective bubble and the swath of space beyond.
Voyager 1 is over 24 billion kilometres from Earth, while Voyager 2 is more than 20.9 billion kilometres away.