Goals: Like Venera 4, Venera 5 was to analyze the atmosphere of Venus while descending through it. The launchings of twin spacecraft Venera 5 and 6 were timed so they would arrive at Venus one day apart, allowing for some cross-calibration of data. The parachutes on the atmospheric probes were 2/3 as large as those used for Venera 4 to allow a faster descent. It was hoped that this would enable them to reach lower altitudes before being crushed or having their electronics disabled by heat.
Accomplishments: The strategy did not work. Venera 5 did fall faster, and thus took measurements for only 53 minutes before ceasing transmission at an altitude of about 24 to 26 km, about the same altitude as Venera 4. Data the probe transmitted suggested that the temperature at the surface was 530°C and atmospheric pressure at the surface was 140 times that of Earth, both of which are considerably higher than current estimates (see Venus Express). Analysis of the mostly carbon dioxide atmosphere was in good agreement with Venera 4.