What discoveries were made thanks to Pioneer orbiter data?

Question

Based on the Wikipedia page Pioneer Venus Orbiter (also known as Pioneer Venus 1, Pioneer 12, 1978-051A) there were quite a few scientific instruments on board. But what scientific results were extracted from the data collected? What did we discover about Venus with Pioneer?

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Note: I hesitated to post this question on the Space Exploration Stackexchange, but since the question is about the characteristics of Venus and the science done with the probe, but not about the probe itself, I figured it was a better fit for this site.

Answer 1

The NASA Pioneer Venus Orbiter mission was planned for a minimum duration of 243 days to cover all Venus longitudes, but eventually sent data for about 14 years.

Some of the major results are:

• The Venus International Reference Atmosphere (VIRA), a detailed model of the atmosphere of Venus, was first published in 1985 using data from the Pioneer Venus Orbiter and the Soviet Venera missions, an inspiring example of scientific collaboration during the cold war. It was later updated using data from the late Soviet Veneras and the ESA Venus Express.

  VIRA consists of the following components: (1) Models of the structure of the atmosphere of Venus up to 100 km altitude, (2) Circulation of the atmosphere up to 100 km altitude, (3) Particulate matter in the Venus atmosphere, (4) Models of Venus neutral upper atmosphere: structure and composition (from 100 to 250 km altitude), (5) Composition of the atmosphere below 100 km altitude, (6) Structure and composition of clouds on Venus, (7) Solar and thermal radiation in the Venus atmosphere, (8) The Venus ionosphere.

• Thermal equilibrium model of Venus including variation of the radiative flux with height and the greenhouse behavior

• Venus magnetic field observations

• Interaction of solar wind with Venus

• Venus surface and interior studies using the Orbiter Radar (ORAD) instrument

• Gamma ray bursts catalog observed in outer space by the Pioneer Venus Orbiter

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