![A small dark cylinder.](https://science.nasa.gov/wp-content/uploads/2024/02/lightweight-radioisotope-heater-unit-2.jpg?w=4096&format=jpeg)
Lightweight Radioisotope Heater Unit
Radioisotope Heater Units (RHUs) are small devices that use the decay of plutonium-238 to provide heat to keep a spacecraft's components and systems warm so that the equipment can survive long enough in the cold space environment to complete its mission.
Credits: U.S. Department of Energy
Image CreditU.S. Department of Energy
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