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Mariner program

The Mariner series of spacecraft were interplanetary probes designed to investigate Mars, Venus, and Mercury. The program included a number of firsts, including the first planetary flyby, the first planetary orbiter, and the first gravity assist.

Of the ten vehicles in the Mariner series, seven were successful and the other three were lost. The planned Mariner 11 and 12 vehicles evolved into Voyager 1 and Voyager 2.

Mariner 1 and Mariner 2 - As the first spacecraft to fly by another planet, Mariner 2 was built as a backup to Mariner 1, which failed shortly after launch to Venus. The Mariner 2 spacecraft was launched on August 27, 1962, sending it on a 3½-month flight to Venus.

Mariner 3 and Mariner 4 - The Mariner 4 spacecraft gave the first glimpse of Mars at close range. Launched on November 28, 1964, Mariner 4 was the fourth in a series of spacecraft used for planetary exploration in a flyby mode and represented the first successful flyby of the planet Mars. A sister ship, Mariner 3, was launched three weeks earlier than Mariner 4, but was lost when the launch vehicle's nose fairing failed to jettison. Mariner 5 - The Mariner 5 spacecraft launched to Venus on June 14, 1967 and arrived in the vicinity of the planet in October 1967. Mariner 5 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. Mariner 6 and 7 - Mariners 6 and 7 were identical teammates in a two-spacecraft mission to Mars. Mariners 6 and 7 were designed to fly over the equator and southern hemisphere of the planet Mars. Mariner 6 was launched on February 24, 1969, followed by Mariner 7 on March 27, 1969. Mariner 8 and Mariner 9 - The first artificial satellite of Mars was Mariner 9, launched in May 1971. In November 1971, the spacecraft entered Martian orbit and began photographing the surface and analyzing the atmosphere with its infrared and ultraviolet instruments. The mission originally consisted of two spacecraft designed to simultaneously map the Martian surface, but the identical Mariner 8 vehicle was lost in a launch vehicle failure. Mariner 10 - The Mariner 10 spacecraft launched on November 3, 1973. Mariner 10 was the first spacecraft to use a gravity assist trajectory, accelerating as it entered the gravitational influence of Venus, then being flung by the planet's gravity onto a slightly different course to reach Mercury. It was also the first spacecraft to encounter two planets at close range.