Editing Pioneer Venus project (section)

===Orbiter===
{{main|Pioneer Venus Orbiter}}

[[File:Pioneer Venus orbiter.jpg|thumb|Pioneer Venus Orbiter]][[File:Venuspioneeruv.jpg|thumb|Cloud structure in [[Atmosphere of Venus|the Venusian atmosphere]] in 1979, revealed by ultraviolet observations by [[Pioneer Venus Orbiter]]]]
The orbiter was launched on May 20, 1978 on an [[Atlas-Centaur]] rocket. The orbiter's mass was {{convert|517|kg|abbr=on}}.<ref name="Intro">{{cite web |url=http://nssdc.gsfc.nasa.gov/planetary/pioneer_venus.html |title=Pioneer Venus Project Information |work=NASA Goddard Space Flight Center |access-date=August 17, 2016 }}</ref> The Pioneer Venus Orbiter was inserted into an elliptical orbit around Venus on December 4, 1978. It carried 17 experiments (with a total mass of 45&nbsp;kg):<ref name="Intro" /> 
*a cloud photopolarimeter to measure the vertical distribution of the clouds 
*a surface radar mapper to determine topography and surface characteristics 
*an infrared radiometer to measure IR emissions from the Venus atmosphere 
*an airglow ultraviolet spectrometer to measure scattered and emitted UV light 
*a neutral mass [[spectrometer]] to determine the composition of the upper atmosphere 
*a [[solar wind]] plasma analyzer to measure properties of the solar wind 
*a [[magnetometer]] to characterize the magnetic field at Venus 
*an electric field detector to study the solar wind and its interactions 
*an electron temperature probe to study the thermal properties of the [[ionosphere]] 
*an ion [[mass spectrometer]] to characterize the ionospheric ion population 
*a charged particle retarding potential analyzer to study ionospheric particles 
*two radio science experiments to determine the gravity field of Venus 
*a radio occultation experiment to characterize the atmosphere 
*an atmospheric drag experiment to study the upper atmosphere 
*a radio science atmospheric and [[solar wind turbulence]] experiment 
*a gamma ray burst detector to record [[gamma-ray burst]] events

In May 1992 the orbiter began the final phase of its mission, in which the periapsis was held between 150 and 250&nbsp;km until the fuel ran out and atmospheric entry destroyed the spacecraft in August 1992.<ref name="Intro"/>