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")
On December 14, 1964, Mariner 2 successfully performed the first planetary encounter of a space probe when it passed within 35,000 kilometers of the planet Venus. This probe surveyed Venus revealing that this planet has a very hot surface blanketed by a thick cloud cover.
The design of Mariner 2 was based off the Ranger Block I space probe. This spacecraft was launched into space on an Atlas-Agena rocket.
The schematic of the Mariner 2 spacecraft was from the archives of the National Aeronautics and Space Administration - Jet Propulsion Laboratory.