A Solar panel, or solar platform, was a piece of advanced energy generation technology aboard NASA's Mariner 2, Nimbus 1, and Ranger 5 space probes when they were launched in the mid-20th century. Solar pannels were also included in the International Space Station.
Schematics of the Mariner 2, Nimbus 1, and Ranger 5 spacecraft depicting the locations of the solar panels was stored in the USS Enterprise's library computer database. This database was accessed by the Talosians in 2254. (TOS: "The Cage")