A Voyager Radioisotope Thermoelectric Generator (RTG)

Each of NASA's Voyager probes are equipped with three radioisotope thermoelectric generators (RTGs), including the one shown here before launch at NASA's Kennedy Space Center in Florida. 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.