Mission Type: Flyby, Lander
Launch Vehicle: 8K82K + Blok DM (Proton-K no. 296-02 / Blok DM no. 4L)
Launch Site: NIIP-5 / launch site 81P
Spacecraft Mass: 4,461 kg
Spacecraft Instruments:
Flyby bus: 1) plasma spectrometer; 2) Konus gamma-ray detector; 3) Sneg-2MZ gamma- and x-ray burst detector; 4) ultraviolet spectrometer; 5) magnetometer; 6) solar wind detectors; and 7) cosmic-ray detectors
Lander: 1) imaging system; 2) Sigma gas chromatograph; 3) mass spectrometer; 4) gamma-ray spectrometer; 5) Groza lightning detector; 6) temperature and pressure sensors; 7) nephelometer; 8) anemometer; 9) optical spectrophotometer; 10) remote soil collector; 11) x-ray fluorescence cloud aerosol analyzer; and 12) Arakhis x-ray fluorescence spectrometer and drill
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.

Venera 12 was the identical sister craft to Venera 11. Launched successfully towards Venus, the spacecraft performed two midcourse corrections on 21 September and 14 December 1978. As with its twin, two days prior to the planetary encounter, the flyby probe released its lander.

On 21 December, the lander entered the Venusian atmosphere at a velocity of 11.2 kilometers per second and performed a descent profile almost identical to that of the earlier Veneras 9 and 10 in 1975.

The lander safely touched down at 03:30 UT on 21 December 1978 after a descent lasting about an hour. Landing coordinates were 7° south latitude and 294° longitude, about 800 kilometers from its twin.

From the ground, the probe relayed data for a record 110 minutes, although like Venera 11, the spacecraft suffered two major failures: its soil sample delivery instrument failed to deposit the soil appropriately for scientific analysis; and lens covers on the imaging system failed to release, effectively rendering the color imaging system useless.

The flyby probe passed by the planet at a range of 35,000 kilometers after performing its data transmission mission and then entered heliocentric orbit.