Launched on July 1969 through Dec. 7, 1972 on the Apollo missions to the moon, the RPS-powered Apollo Lunar Surface Experiment Package studied moon quakes and other lunar science. These experiments revealed that the moon is not a geologically dead world.
The SNAP-27 RTG power source enabled the experiments to outlive their design lifetime. ALSEP's collection of geophysical instruments were designed to monitor the environment of each Apollo landing site for at least a year after the astronauts had departed. They ended up working for up to 8 years, and the experiments permanently shut down by Mission Control on Sept. 30, 1977.
For more on ALSEP, visit the Apollo Surface Experiments page, or https://www.nasa.gov/feature/50-years-ago-first-apollo-lunar-surface-experiment-package-accepted.