MHW-RTG

[1] The Voyager generators continue to function more than 45 years into the mission.

[2] Each RTG has a total weight of 37.7 kg, including about 4.5 kg of Pu-238[3] and uses 24 pressed plutonium-238 oxide spheres to provide enough heat to generate approximately 157 watts of electrical power initially – halving every 87.7 years.

[5] Conversion of the decay heat of the plutonium to electrical power uses 312 silicon-germanium (SiGe) thermoelectric couples.

Collectively, the RTGs supply each Voyager spacecraft with 470 watts at launch.

Subsequent US spacecraft used the GPHS-RTG, which used similar SiGe thermoelectric devices but a different packaging of the fuel.