Mariner 2 was an American Mariner program space probe that was in service with NASA in the mid-20th century. A schematic of this spacecraft was stored in the USS Enterprise's library computer database. This database was accessed by the Talosians in 2254.
The Mariner 2 was equipped with several pieces of advanced technology for the period, including a magnetometer sensor, omnidirectional antenna, radiometer reference horns, radiometer, temperature control shield, solar plasma detector, temperature control louvers, solar panels, command antenna, cosmic dust detector, high-gain antenna, long range Earth sensor, primary sun sensor, ion chamber, particle flux detector, and secondary sun sensor. (TOS: "The Cage")