Mission Type: Flyby
Launch Vehicle: 8K78
Launch Site: NIIP-5 / launch site 1
Spacecraft Mass: 950 kg
Spacecraft Instruments:
1) imaging system
2) ultraviolet spectrograph
3) ultraviolet and infrared spectrophotometer
4) meteoroid detectors
5) radiation sensors (cosmic rays, solar wind)
References:
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, by Asif A. Siddiqi, NASA Monographs in Aerospace History No. 24

NSSDC Master Catalog, http://nssdc.gsfc.nasa.gov/nmc/

This third-generation deep space probe had originally been slated for a Mars flyby in late 1964 but could not be prepared on time. Instead, Soviet designers diverted the mission for a simple lunar flyby in 1965 to test its basic systems and photograph the far side of the Moon.

After a successful translunar injection burn, Zond 3 approached the Moon after only a 33-hour flight. Its imaging mission began on 20 July at a range of 11,570 kilometers from the near side of the Moon.

The camera system used a similar system to that of Luna 3, with onboard exposure, development, fixing, and drying prior to scanning for transmission to Earth. In total, the spacecraft took twenty-five visual and three ultraviolet images during its flyby. The closest approach was to 9,220 kilometers. These pictures were successfully transmitted back to Earth on 29 July, nine days after Zond 3's lunar encounter, when it was 2.2 million kilometers from Earth.

Further communications sessions occurred on 23 October (involving photo transmissions) when Zond 3 was 31.5 million kilometers from Earth. The last contact was sometime in early March 1966, when the spacecraft was 153.5 million kilometers away.

During the mission, it had photographed the unseen 30 percent of the far side of the Moon. Zond 3 also demonstrated successful course correction using both solar and stellar orientation, a first for a Soviet spacecraft.