From 1961 to 1984 the Soviet Union carried out a program of exploration of Venus using Venera spacecraft. In 1967 Venera 4 entered the atmosphere and obtained direct measures of temperature and pressure (Avduevskii, V.S., et al.). Avduevsky, V. S., Marov, M. Y and Rozhdestvensky, M. K., reported a surface temperature 0f 770+/-60K and surface pressure of 97 atmospheres derived from Venera 5 and 6 data.
Venera 7 & 8 landed and transmitted data for about an hour. They did not carry cameras but returned photometric data. Kerzhanovich, V. V., Marov, M. Ya. And Rozhdestvensky, M. K., reported winds of 40-50 m/sec at 40-50 km altitude and surface winds of 0- 2.5 m/sec based on Venera 5, 6, and 7 data.
Ainsworth, J. E. and Herman, J. R.,'s obtained similar winds for Venera 7 and 8. They reported that the lower boundary of the horizontal retrograde '4-day' wind is defined by a 50-60% decrease in wind speed at about 44 km and that the winds are fairly constant, ranging from 15 to 40 m/s, down to 18 km. Below that the winds rapidly drop off to about 0.1 m/s near the surface.
Results from later Veneras were more widely popularized with transmission of images of the surface from Venera 9 and 10 in 1975 and of colored images by Venera 13 and 14 in 1982. Venera 15 and 16 concentrated on radar and IR measurements.
See PIONEER Venus NASA SP-461
, Chapter 7 pages169-190
Avduevskii, V.S., et al., Venus (A83-37401 17-91). Tucson, AZ, University of Arizona Press, 1983, p. 280-298.
Avduevsky, V. S., Marov, M. Y and Rozhdestvensky, M. K., Tentative Model of the Venus Atmosphere Based on the Measurements of Veneras 5 and 6. Journal of Atmospheric Sciences, vol. 27, Issue 4, pp.561-568. 1070
Kerzhanovich, V. V., Marov, M. Ya. And Rozhdestvensky, M. K., Data on Dynamics of the Subcloud Venus Atmosphere from Venera Spaceprobe Measurements. Icarus, Volume 17, Issue 3, p. 659-674, 1972. DOI: 10.1016/0019-1035(72)90030-9
Ainsworth, J. E. and Herman, J. R., Venus wind and temperature structure: The Venera 8 data, Journal of Geophysical Research, Volume 80, Issue 1, p. 173, 1975. DOI: 10.1029/JA080i001p00173
See NSSDCA Photo Gallery for images of the Venus surface