Date: 18 Jul 1965
Zond 3 was launched from a Tyazheliy Sputnik (65-056B) Earth-orbiting platform towards the moon and interplanetary space. The spacecraft was equipped with an f106 mm camera and TV system that provided automatic in-flight film processing.
On 20 July 1965, lunar flyby occurred approximately 33 hours after launch at a closest approach of 9,200 km. 25 pictures of very good quality were taken of the lunar farside from distances of 11,570 to 9,960 km over a period of 68 minutes. The photos covered 19,000,000 square km of the lunar surface. Photo transmissions by facsimile were returned to Earth from a distance of 2,200,000 km and were re-transmitted from a distance of 31,500,000 km (some signals still being transmitted from the distance of the orbit of Mars), thus proving the ability of the communications system. After the lunar flyby, Zond 3 continued space exploration in a heliocentric orbit.
The spacecraft design was similar to Zond 2; in addition to the imaging equipment, it carried a magnetometer, ultraviolet (0.25 - 0.35 micron and 0.19 - 0.27 micron) and infrared (3 - 4 micron) spectrographs, radiation sensors (gas-discharge and scintillation counters), a radiotelescope, and a micrometeoroid instrument. It also had an experimental ion engine.
It is believed that Zond 3 was initially designed as a companion spacecraft to Zond 2 to be launched to Mars during the 1964 launch window. The opportunity to launch was missed, and the spacecraft was launched on a Mars trajectory, (although Mars was no longer attainable) as a spacecraft test.