Mission Type: Flyby
Launch Vehicle: Proton booster plus upper stage and escape stages; 8K82K + Blok D (Proton-K no. 250-01)
Launch Site: Tyuratam (Baikonur Cosmodrome), USSR; NIIP-5 / launch site 81L
Spacecraft Mass: c. 5,375 kg
Spacecraft Instruments: 1) solar wind collector packages and 2) imaging system
References:
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

National Space Science Data Center, http://nssdc.gsfc.nasa.gov/

Solar System Log by Andrew Wilson, published 1987 by Jane's Publishing Co. Ltd.

Zond 8 was the last in the series of circumlunar spacecraft designed to rehearse a piloted circumlunar flight. The project was initiated in 1965 to compete with the Americans in the race to the Moon, but lost its importance once three astronauts circled the Moon on the Apollo 8 mission in December 1968.

After a midcourse correction on 22 October at a distance of 250,000 km from Earth, Zond 8 reached the Moon without any apparent problems, circling its target on 24 October at a range of 1,200 km. The spacecraft took black-and-white photographs of the lunar surface during two separate sessions.

After two midcourse corrections on the return leg, Zond 8 flew a return over Earth's northern hemisphere instead of the standard southern approach profile, allowing Soviet ground control stations to maintain near-continuous contact with the ship. The guidance system evidently malfunctioned on the return leg, and the spacecraft performed a simple ballistic (instead of a guided) reentry into Earth's atmosphere. The vehicle's descent module splashed down safely in the Indian Ocean at 13:55 UT on 27 October about 730 km southeast of the Chagos Islands, 24 km from its original target point.