Two black cylinders stacked on top of each other.

Voyager Radioisotope Thermoelectric Generator

Each of NASA's Voyager probes are equipped with three Radioisotope Thermoelectric Generators (RTGs), including the one shown here at NASA's Kennedy Space Center in Florida. The RTGs provide power for the spacecraft by converting the heat generated by the decay of plutonium-238 into electricity. Launched in 1977, the Voyager mission is managed for NASA by the agency's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California.

Credits: NASA/JPL-Caltech