Goals: Pioneer Venus 2, the twin to Pioneer Venus 1, comprised a main bus, a large probe (316.5 kg), and three identical small probes, all of which were designed to collect
data during independent atmospheric entry into Venus. Each probe was shaped like a cone and not designed to survive past surface impact.
Accomplishments: After a course correction on 16 August 1978, Pioneer Venus 2 released the 1.5-m diameter large probe on 16 November 1978, at about 11.1 million km from the planet. Four days later, the bus released the three small probes while 9.3 million km from Venus. All five components reached the Venusian atmosphere on 9 December 1978, with the large probe entering first.
Data from the probes indicated that between 10 and 50 km, there is almost no convection in the Venusian atmosphere. Below a haze layer at 30 km, the atmosphere appears to be relatively clear. Amazingly, two of three probes survived the hard impact. The so-called Day Probe transmitted data from the surface for 67.5 minutes before succumbing to the high temperatures and power depletion.