Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere. Source: Internet
Venera landers in 1975 and 1982 returned images of a surface covered in sediment and relatively angular rocks. citation The surface was mapped in detail by Magellan in 1990–91. Source: Internet
In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. Source: Internet
Radio occultation data from Mariner 5 helped to understand the temperature and pressure data returned by the Venera 4 lander, which arrived at Venus shortly before it. Source: Internet
Several lines are missing due to a simultaneous transmission of the scientific data On 18 October 1967, the Soviet Venera 4 successfully entered the atmosphere and deployed science experiments. Source: Internet
The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to Earth for 23 minutes. Source: Internet