Venus has an extremely dense atmosphere, which consists mainly of carbon dioxide and a small amount of nitrogen. The atmospheric mass is 93 times that of Earth's atmosphere, while the pressure at the planet's surface is about 92 times that at Earth's surface — a pressure equivalent to that at a depth of nearly 1 kilometer under Earth's oceans. The density at the surface is 65 kg/m³ (6.5% that of water). The CO2-rich atmosphere, along with thick clouds of sulfur dioxide, generates the strongest greenhouse effect in the Solar System, creating surface temperatures of over 460 °C (860 °F).[39] This makes the Venusian surface hotter than Mercury's, which has a minimum surface temperature of −220 °C and maximum surface temperature of 420 °C,[40] even though Venus is nearly twice Mercury's distance from the Sun and thus receives only 25% of Mercury's solar irradiance. The surface of Venus is often said to resemble traditional accounts of Hell.[41]

http://en.wikipedia.org/wiki/Venus#Atmosphere_and_climate

On October 20, 1975, the lander spacecraft was separated from the orbiter, and landing was made with the Sun near zenith at 05:13 UTC on October 22. Venera 9 landed within a 150 km radius of 31.01°N 291.64°E, near Beta Regio, on a steep (20°) slope covered with boulders (suspected to be the slope of the tectonic rift valley, Aikhulu Chasma). The entry sphere weighed 1,560 kg (3,440 lb) and the surface payload 660 kg (1,455 lb).[3]

It was the first spacecraft to return an image from the surface of another planet. The Soviet space program had far more success with Venus landers than Mars landers, possibly because the mechanics of landing on Venus involve fewer steps than Mars due to the much thicker atmosphere.

A system of circulating fluid was used to distribute the heat load. This system, plus pre-cooling prior to entry, permitted operation of the lander for 53 minutes after landing, at which time radio contact with the orbiter was lost as the orbiter moved out of radio range.[4] During descent, heat dissipation and deceleration were accomplished sequentially by protective hemispheric shells, three parachutes, a disc-shaped drag brake, and a compressible, metal, doughnut-shaped landing cushion. The landing was about 2,200 km from the Venera 10 landing site.

Venera 9 measured clouds that were 30–40 km thick with bases at 30–35 km altitude. It also measured atmospheric chemicals including hydrochloric acid, hydrofluoric acid, bromine, and iodine. Other measurements included surface pressure of about 90 atmospheres (9 MPa), temperature of 485 °C, and surface light levels comparable to those at Earth mid-latitudes on a cloudy summer day. Venera 9 was the first probe to send back black and white television pictures from the Venusian surface showing shadows, no apparent dust in the air, and a variety of 30 to 40 cm rocks which were not eroded. Planned 360-degree panoramic pictures could not be taken because one of two camera lens covers failed to come off, limiting pictures to 180 degrees. This failure recurred with Venera 10.

• Temperature and pressure sensors
• Accelerometer
• Visible / IR photometer - IOV-75
• Backscatter and multi-angle nephelometers - MNV-75
• P-11 Mass spectrometer - MAV-75
• Panoramic telephotometers (2, with lamps)
• Anemometer - ISV-75
• Gamma ray spectrometer - GS-12V
• Gamma ray densitometer - RP-75
• Radio Doppler experiment

Don P. Mitchell recently came across the original Venera imaging data while researching the Soviet Venus program, and reconstructed the images using modern image processing software.

http://en.wikipedia.org/wiki/Venera_9

http://www.ourbabynamer.com/meaning-of-Venera.html