Kosmos 359

Kosmos 359 was an unmanned Soviet probe launched on 22 August 1970. The probe's intended purpose was to explore Venus, but an error caused the final-stage rocket to malfunction. This left the craft trapped in an elliptical orbit around Earth for 410 days before orbital decay and atmospheric entry. Kosmos 359 was launched five days after Venera 7 and had an identical design; had the craft not suffered a mission-ending failure, it would have landed on Venus shortly after Venera 7. To publicly acknowledge the failure of the attempted Venus lander would be a public relations disaster for the Soviet space program; after the mission failed, the Venera spacecraft was renamed Kosmos 359 in order to conceal the mishap from the public.

Design
The lander was designed to be able to survive atmospheric pressures of up to 180 bar and temperatures of 580 C. This was significantly greater than what was expected to be encountered, but significant uncertainties as to the surface temperatures and pressure of Venus resulted in the designers opting for a large margin of error. The degree of hardening added mass to the probe, which limited the amount of mass available for scientific instruments on the probe and the interplanetary bus.

Rocket malfunction
After reaching orbit, the main upper stage engine ignited late and shut down early after running for only twenty-five seconds. The error was ultimately attributed to an error in the DC transformer of the power supply system.

Experiments
Kosmos 359 carried a limited set of scientific instruments, including a solar wind detector, cosmic-ray detector, resistance thermometer, and aneroid barometer.