Mission Type: Flyby
Launch Vehicle: 8K82K + Blok D (Proton-K no. 232-01)
Launch Site: Tyuratam (Baikonur Cosmodrome), , USSR, NIIP-5 / launch site 81L
Spacecraft Mass: About 5,375 kg
Spacecraft Instruments: Unknown
Spacecraft Dimensions: Cylindrical capsule approx. 4.5 m in length and 2.2 to 2.72 m in diameter, with 2 solar panels on opposite sides of the body spanning a total of about 9 m
Spacecraft Power: Solar panels
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.

The Soviets decided to send this next 7K-L1 spacecraft, not on a circumlunar flight, but about 330,000 kilometers into deep space in the opposite direction of the Moon in order to test the main spacecraft systems without the perturbing effects of the Moon (much like the Surveyor model test flights in 1965 and 1966).

The spacecraft was successfully boosted on its trajectory and reached an apogee of 354,000 kilometers. During the flight, although a key attitude-control sensor worked only intermittently, controllers managed to aim the spacecraft for a guided reentry back into Earth's atmosphere. Unfortunately, the same sensor failed at reentry, preventing the vehicle from maintaining stable orientation. Instead, Zond 4 began to carry out a direct ballistic reentry for landing in the Indian Ocean. An emergency destruct system, however, destroyed the returning capsule over the Gulf of Guinea to prevent foreign observers from recovering the wayward spacecraft.