Mariners 3 and 4 Spacecraft

Launch (Mariner 4): November 28, 1964
Flyby (Mariner 4): July 14, 1965
Mass: 261 kilograms (575 pounds)
Science instruments: Camera with digital tape recorder (about 20 pictures), instruments studying cosmic dust, solar plasma, trapped radiation, cosmic rays, magnetic fields, radio occultation and celestial mechanics

Mariners 3 and 4 were built by NASA and designed to perform a flyby of Mars with three main objectives:

1. To conduct field and particle experiments in interplanetary space, including measurements of the Martian magnetic field, cosmic dust and cosmic rays, and the solar wind.
2. To provide close range images of Mars in order to provide us with the most detailed surface pictures ever obtained of the planet, hopefully revealing geologic and atmospheric processes.
3. As interplanetary probes were still a new technology, the mission would provide experience in operational and engineering techniques required for long term interplanetary missions.

The Mariners launch came some 4 years after the USSR launched their first attempted unmanned mission to Mars, which were unfortunately unsuccessful in achieving flyby. Mariner 3 launched on November 5, 1964, but its shroud encasing the spacecraft atop its rocket did not open successfully and Mariner 3 did not make it to Mars. Three weeks later however, Mariner 4 launched successfully on November 28, 1964 and flew past, achieving the first successful Mars flyby on July 14, 1965. It collected the close-up photographs of Mars and returned 21 photos to Earth. Mariner 4's successful eight-month voyage gave scientist pictures of Mars' geographical terrain and new data on Mars, notably the lunar-type impact craters topping the Martian surface. But more importantly, Mariner 4 gave NASA experience for further missions to be conducted.