Venera 8

Description

Venera 8 was one of a pair of Venus atmospheric lander probes designed for the spring 1972 launch window. The other mission (Cosmos 482) failed to leave Earth orbit. The objectives were to make a more sophisticated set of scientific measurements at the Venus surface, including studies of the Venus regolith.

Spacecraft and Subsystems

The Venera 8 spacecraft comprised a bus and lander probe. The lander probe was a spherical pressure vessel with a mass of 495 kg of similar design to the Venera 7 probe. It had a top shell that would be jettisoned on atmospheric entry to deploy the 2.5 square meter parachute and expose the instruments. The probe was battery powered. Its instrumentation included temperature, pressure, and light sensors as well as an altimeter, anemometer, gamma-ray spectrometer, gas analyzer, and radio transmitters. The bus contained a cosmic ray detector, solar wind detector, and ultraviolet spectrometer.

Mission Profile

Venera 8 launched on 27 March 1972 at 04:15:01 UT. The spacecraft took 117 days to reach Venus with one mid-course correction on 6 April 1972. Before reaching Venus the probe interior was cooled to -15 degrees C. It separated from the bus on 22 July 1972 at 07:44 UT and entered the atmosphere at 08:37 UT. Descent speed was reduced from 11 km/sec at entry to about 250 meters/s at 67 km altitude by aerobraking. The parachute opened in reefed mode at an altitude of 60 km, and a refrigeration system was used to cool the interior components. Venera 8 transmitted data during the descent from instrument turn-on at 50 km. At 30 km altitude the parachute was fully opened. A decrease in illumination was noted at 35 to 30 km altitude and wind speeds of less than 1 km/s were measured below 10 km. Venera 8 landed at 09:32 UT at 10 degrees south, 335 degrees east, about 500 km from the morning terminator on the day side. It continued to send back data for 63 minutes after landing before failing due to the harsh surface conditions.

The probe confirmed the earlier data on the high Venus surface temperature and pressure (470 degrees C, 90 atmospheres) returned by Venera 7, and also measured the light level as being suitable for surface photography, finding it to be similar to the amount of light on Earth on an overcast day with roughly 1 km visibility. The first measurements of the surface regolith of Venus were returned, and a profile of the cloud layer, including detection of sulfuric acid, was made.

Upper spacecraft image courtesy of Alexander Chernov - all rights reserved. Lower image from Lavochkin Museum.