The Mariner 5 spacecraft was the fifth in a series of spacecraft used for planetary exploration in the flyby mode. Mariner 5 was a refurbished backup spacecraft for the Mariner 4 mission and was converted from a Mars mission to a Venus mission. The spacecraft was fully attitude stabilized, using the Sun and Canopus as references. A central computer and sequencer subsystem supplied timing sequences and computing services for other spacecraft subsystems.

Mariner 5 was launched on June 14, 1967, and arrived in the vicinity of Venus on October 19, 1967. The spacecraft carried a complement of experiments to probe Venus's atmosphere with radio waves, scan its brightness in ultraviolet light, and sample the solar particles and magnetic field fluctuations above the planet. The closest flyby distance was 3,990 kilometers (2,480 miles) and, with more sensitive instruments than its predecessor, Mariner 5 was able to shed new light on the hot, cloud-covered planet and on conditions in interplanetary space. The spacecraft also advanced the techniques of building and operating interplanetary spacecraft, as had each Mariner before it. All operations of Mariner 5 were closed out in November 1967.

Mariner 5
The Mariner 5 spacecraft was launched June 14, 1967, and flew by Venus on October 19 of that year at a distance of 4,000 kilometers (2,480 miles). (Courtesy NASA/JPL)