On July 22, 1972, at 11:37 am, the Venera-8 automatic interplanetary station (AMS) entered the atmosphere of the second planet of the solar system. In honor of the half-century anniversary of this event, Roskosmos and NPO them. S. A. Lavochkin published a documentary film, which tells regarding the Venera-7 and Venera-8 devices.
Image source: roscosmos.ru
The Venera-7 mission helped Soviet specialists clarify information regarding what was happening on the planet and accordingly change the design of the next apparatus: the design pressure was reduced from 150 to 105 atmospheres, and the temperature from 540 ° C to 493 ° C.
Venera-8 launched from the Baikonur Cosmodrome on March 27, 1972, and the journey to the planet took 117 days. Aerodynamic braking slowed down the speed of the AMS relative to the planet from 11.6 km/s to 250 m/s; at an altitude of 55 km above its surface, a parachute was deployed, the further flight lasted 55 minutes. The spacecraft landed at 12:32 pm, 500 km from the morning terminator, the dividing line between the shadow and illuminated parts of the planet.
Broadcast telemetry “Venera-8” was carried out throughout the entire time of landing and another 50 minutes following its completion. Measurements of atmospheric parameters basically repeated the data of the previous mission: temperature 470 ± 8 ° C, pressure 90 ± 1.5 atmospheres. During the descent, the ammonia content in the atmosphere was measured twice – it turned out to be in the range from 0.01% to 0.1%. Illumination on the surface at an angle of the Sun of 5.5° was 350 ± 150 lux – such an indicator is observed on Earth on a cloudy day.
Subsequently, calculations were made, according to which, with the Sun at its zenith, the illumination on the surface of Venus should reach from 1000 to 3000 lux. This is regarding 10 times lower than that taken in the shadows on Earth on a clear day. However, under a high layer of clouds, the planet’s atmosphere is transparent enough to be photographed.
The specialists also assessed the wind speed at different heights, for which it was necessary to measure the radial component of the device’s velocity using the Doppler shift of the signal: at a height of 50 km it turned out to be 50 m/s, and at a height of 0 to 11 km it was from 0 to 2 m/s With. This indicates the latitudinal wind, which is directed from the terminator to the day side – in the same direction as the rotation of the planet.
The radio altimeter helped in assessing the dielectric constant and density of the soil on Venus – it is loose, and the density was 1.4 g / cm³. The gamma-ray spectrometer made it possible to estimate the content of radioactive elements in the soil: their content and ratio approximately correspond to terrestrial granite rocks.
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