Venera 7

Description

Venera 7 was one of two identical spacecraft launched to Venus during the August 1970 opportunity. The other mission (Cosmos 359) failed to leave Earth orbit. The objectives of the missions were to return data from the Venus atmosphere, make a landing on the surface, and continue to return data after landing. Venera 7 was the first spacecraft to return data after landing on another planet.

Spacecraft and Subsystems

The spacecraft was very similar in design to Venera 5 and 6, with a bus holding a spherical lander probe. The probe was designed to withstand higher pressures and temperatures, as well as the shock of landing, through the use of a single spherical shell with no seams, welds, or holes. Titanium was used in the construction of the pressure vessel, and it was lined with shock absorbing material. The result was a more massive probe, 490 kg. An even smaller parachute (2.5 square meters) was used to speed the descent. The lander held a resistance thermometer and an aneroid barometer. The bus held a solar wind detector and a cosmic ray detector.

Mission Profile

Venera 7 was launched on 17 August 1970 at 05:38:22 UT into an Earth parking orbit and then from a Tyazheliy Sputnik towards Venus. Two mid-course corrections were made, on 2 October and 17 November. The lander probe was allowed to cool to -8 degrees C before atmospheric entry. The Venera 7 probe separated from the bus and entered the nightside atmosphere of Venus on December 15, 1970 at 04:58:44 UT. After aerodynamic braking, the top hatch was blown and the parachute system was deployed at about 60 km altitude. The capsule antenna was extended, and signals return commenced. Six minutes later the parachute ripped, and then collapsed, leaving the probe to fall towards the surface for another 29 minutes. The probe impacted on the Venus surface at 05:34:10 UT at about 17 meters/sec and the signals weakened, reached full strength for about one second, and then seemingly ceased. Later analysis of the recorded radio signals revealed that the probe had survived the impact and continued transmitting a weak signal for another 23 minutes. It is believed that the spacecraft may have bounced upon impact and come to rest on its side, so the antenna was not pointed towards Earth. The pressure sensor had failed during the descent, but the temperature sensor showed a steady reading of 475 C at the surface, and a pressure of 92 bar with a wind of 2.5 meters/sec was extrapolated from other measurements. The landing point was 5 degrees S, 351 degrees E.

Spacecraft image for illustrative purposes, not in the public domain.