Mission Type: Atmospheric Probe
Launch Vehicle: Modified SS-6 (Sapwood) with 2nd-generation upper stage + escape stage, 8K78M
Launch Site: Tyuratam (Baikonur Cosmodrome), USSR, NIIP-5 / launch site 1
Spacecraft Mass: 405 kg (probe), 1,130 kg (probe and bus)
Spacecraft Instruments:
Probe: 1) radio altimeter; 2) aneroid barometer; 3) eleven gas analyzer cartridges; 4) two resistance thermometers; 5) ionization densitometer; and 6) photoelectric sensors
Bus: 1) magnetometer; 2) cosmic-ray counters; 3) charged-particle traps; 4) ultraviolet photometer
Spacecraft Dimensions: Main bus was about 3.5 m high and 4 m across the deployed solar panels. Probe was a sphere, 1 m in diameter.
Antenna Diameter: 2.3 m (high-gain antenna)
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.

Veneras 5 and 6 were two identical spacecraft designed to penetrate Venus's atmosphere and transmit a variety of scientific data to Earth during descent. The two spacecraft were targeted to reach Venus only a day apart, thus allowing some cross-calibration of data.

Although both spacecraft used a bus-lander system similar to the 1V-type spacecraft (flown as Venera 4), the two new landers (each weighing 405 kilograms) were designed to endure g-loads as high as 450 (as opposed to 300 for their predecessors). The landers also used smaller parachutes for descent, allowing the probes to descend faster through the atmosphere to increase chances of operating close to the surface.

After performing 73 communications sessions with ground control and completing one midcourse correction on 14 March 1966, Venera 5 approached the dark side of Venus on 16 May 1969 and detached its lander, whose speed reduced from 1,100.17 meters per second to 210 meters per second after it hit the Venusian atmosphere at 06:01 UT. One minute later, controllers re-established contact with the lander and began receiving transmitted data on pressure, temperature, and composition of the Venusian atmosphere for 53 minutes.

Contact was lost at an altitude of about 24 to 26 kilometers when the pressure exceeded 26.1 atmospheres. Impact coordinates were 3° south latitude and 18° longitude. Information extrapolated from Venera 5's data suggested that ground temperature and pressure at the Venusian surface were 140 atmospheres and 530°C, respectively.