The Soviet Union sent a series of 16 unmanned Venera probes to study Venus, starting in 1961.
Venera 4, 5 and 6 surveyed the atmosphere, but were destroyed by the planet's extreme pressures and temperatures before they reached the surface.
In 1970 Venera 7 became the first probe to land on another planet and transmitted pressure and temperature data for 23 minutes.
In 1975 Venera 9 and 10 returned the first close-up photographs taken from the surface Venus.
Photo: Venera 7 (NASA)
Soviet probes battle extreme conditions on Venus.
The Russians try to reveal cloudy Venus's secrets.
The Russian Venus probe Venera 4 arrived at the planet in October 1967. As it entered the thick Venusian atmosphere, unexpectedly high pressures destroyed the craft as it descended. However, the probe managed return data to the Earth.
Can the Russians design a spacecraft capable of surviving Venus's extreme pressures?
The Russians took on the challenge of building a probe strong enough to survive the incredibly high atmospheric pressures on Venus. Ultimately they succeeded with Venera 7 in 1970. The subsequent Venera 9 mission returned photographs of the planet's volcanic surface.
The Russians take the first photograph of the planet's surface.
After a series of Venera missions, the Russians built Venera 9, a craft capable of withstanding Venus's searing temperatures and crushing pressures long enough to send back a picture of the surface. Venera 9's 1975 photograph of Venus showed a surface strewn with volcanic rocks.
The Soviet Union saw Venus as a Cold War battleground.
Scientists from the Soviet space programme describe their efforts to study Venus with unmanned probes as their government focussed on the Cold War rivalry with the United States.
Sir Patrick Moore talks about the first Venera images taken from Venus's surface.
In 1975 the Soviet Venera 9 and 10 missions managed to survive the punishing conditions on Venus long enough to return photographs of the rocky world. Sir Patrick talks to Dr Garry Hunt about the probes and the images they returned.
The Venera (Russian: Венера, pronounced [vʲɪˈnʲerə]) series probes were developed by the Soviet Union between 1961 and 1984 to gather data from Venus, Venera being the Russian name for Venus. As with some of the Soviet Union's other planetary probes, the later versions were launched in pairs with a second vehicle being launched soon after the first of the pair.
Ten probes from the Venera series successfully landed on Venus and transmitted data from the surface, including the two Vega program and Venera-Halley probes. In addition, thirteen Venera probes successfully transmitted data from the atmosphere of Venus.
Among the other results, probes of the series became the first man-made devices to enter the atmosphere of another planet (Venera 4 on October 18, 1967), to make a soft landing on another planet (Venera 7 on December 15, 1970), to return images from the planetary surface (Venera 9 on June 8, 1975), and to perform high-resolution radar mapping studies of Venus (Venera 15 on June 2, 1983). The entire series could be considered highly successful. The surface conditions on Venus are extreme, therefore the probes only survived on the surface for a duration of 23 minutes (initial probes) up to about two hours (final probes).