In December 1970, the spacecraft, approached Venus after a rather uneventful flight. On December 15, the VENUS-7 lander separated from its cruise stage and plunged into the planet's atmosphere on the dark side of the planet, which was facing Earth. Unfortunately, scientists on the ground discovered that due to malfunction of a mechanical switch on the probe, the spacecraft had lost the capability to transmit all but a single channel of data. We were lucky, this switch stuck on a temperature reading - temperature data can allow to estimate pressure too, because they are related.
As VENUS-7 descended into the Venusian atmosphere, it continued transmitting temperature data down to an altitude of around 10 meters. Then another disaster struck. At this point, the probe's parachute was lost and the spacecraft plummeted toward the surface of Venus. The mission was seemingly over - the deep-space control station in Crimea was receiving nothing but background noise from the emptiness of space. More stunning was the news a week later, when experts from the Moscow's Institute of Radio Electronics told us that they had been able to discern VENUS-7's signal from the background radio noise recorded after the landing.