Editing Pioneer Venus project

{{Short description|Two spacecraft sent to Venus in 1978}}
{{more citations needed|date=August 2016}}
{{Use American English|date=March 2014}}
{{Use mdy dates|date=March 2020}}

{{Main|Pioneer Venus Orbiter|Pioneer Venus Multiprobe}}
[[File:Arrival of the Pioneer Venus spacecraft at Venus (ARC-1978-AC78-0238).jpg|thumb|Arrival of the Pioneer Venus spacecraft at Venus]]
The '''Pioneer Venus project''' was part of the [[Pioneer program]] consisting of two spacecraft, the [[Pioneer Venus Orbiter]] and the [[Pioneer Venus Multiprobe]], launched to [[Venus]] in 1978.<ref name=":0">{{Cite web|url=https://www.nasa.gov/mission_pages/pioneer-venus/|title=The Pioneer Venus Project|website=[[NASA]]|access-date=2023-03-26}}</ref> The program was managed by [[NASA]]'s [[Ames Research Center]].

The Pioneer Venus Orbiter entered orbit around Venus on December 4, 1978, and performed observations to characterize the [[Atmosphere of Venus|atmosphere]] and surface of Venus.<ref>{{Cite web|url=https://solarsystem.nasa.gov/missions/pioneer-venus-1/in-depth|title=Pioneer Venus 1|website=NASA Solar System Exploration|access-date=2023-03-26}}</ref> It continued to transmit data until October 1992.<ref name=":0" /><ref name="Intro" />

The Pioneer Venus Multiprobe deployed four small probes into the Venusian atmosphere on December 9, 1978.<ref name=":0" /><ref name="Intro" /> All four probes transmitted data throughout their descent to the surface.<ref name="InDepth" /> One probe survived the landing and transmitted data from the surface for over an hour.

==Overview==
The Pioneer mission consisted of two components, launched separately: an orbiter and a multiprobe.
 
===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"/>

===Multiprobe===
{{main|Pioneer Venus Multiprobe}}
[[File:Pioneer Venus Multiprobe spacecraft.jpg|thumb|Pioneer Venus Multiprobe bus and atmospheric probes]]
[[File:Pioneer Venus Orbiter and Multi-Probe - 1978 01565.jpg|thumb|Pioneer Venus Multi-Probe]]
The Pioneer Venus Multiprobe was launched on August 8, 1978 on an Atlas-Centaur rocket. It consisted of a 290&nbsp;kg [[Satellite bus|bus]] which carried one large (315&nbsp;kg) and three small atmospheric probes.  The large probe was released on November 16, 1978 and the three small probes on November 20. All four probes entered the Venus atmosphere on December 9, followed by the bus.

The Pioneer Venus large probe was about 1.5 m in diameter and equipped with 7 science experiments. After deceleration from initial atmospheric entry at about 11.5&nbsp;km/s, a parachute was deployed at 47&nbsp;km altitude. The probe stopped broadcasting when it impacted the surface.<ref name="InDepth" /> The science experiments were:<ref name="Intro"/> 
*a neutral [[mass spectrometer]] to measure the atmospheric composition 
*a [[gas chromatograph]] to measure the atmospheric composition 
*a [[Radiant flux|solar flux radiometer]] to measure solar flux penetration in the atmosphere 
*an infrared radiometer to measure distribution of infrared radiation 
*a cloud particle size spectrometer to measure particle size and shape 
*a [[nephelometer]] to search for cloud particles 
*temperature, pressure, and acceleration sensors

The three small probes were identical to each other, 0.8 m in diameter and 90&nbsp;kg each small probe.<ref name="Intro"/> The small probes were each targeted at different parts of the planet;<ref>[http://nssdc.gsfc.nasa.gov/planetary/pvprobes.html Pioneer Venus Probes]. NASA Goddard Space Flight Center, 2005.</ref>  They had no parachutes and the aeroshells did not separate from the probe. Two of the small probes reached the surface, and one of these, the day probe, continued to broadcast for 67 minutes and 37 seconds after reaching the surface.<ref name="InDepth">NASA. ''[https://solarsystem.nasa.gov/missions/pioneer-venus-2/in-depth/ Pioneer Venus 2]'', NASA Science: Solar System Exploration, February 3, 2021. Retrieved 24 April 2022.</ref>

The Pioneer Venus [[Satellite bus|bus]] also carried two experiments, a neutral [[mass spectrometer]] and an ion mass spectrometer to study the composition of the atmosphere. With no heat shield or parachute, the bus made measurements only to about 110&nbsp;km altitude before burning up.<ref name="Intro"/>

==See also==
{{Portal|Spaceflight}}
* [[1978 in spaceflight]]
* [[Vega program]]
* [[Venera|Venera program]]

==References==
{{reflist}}

==External links==
{{Commons category|Pioneer Venus project}}
* [http://nssdc.gsfc.nasa.gov/planetary/pioneer_venus.html NASA: Pioneer Venus Project Information]
* [https://web.archive.org/web/20080925191131/http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Pioneer_Venus Pioneer Venus Program Page] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1978-078A NSSDC Master Catalog: Spacecraft Pioneer Venus Probe Bus]. (Other components of the mission have their own pages at this site too.)
* [http://nssdc.gsfc.nasa.gov/planetary/pvdata.html Pioneer Venus] specifications at NASA
* "[https://archive.org/details/nasa_techdoc_19900013957 The Pioneer Venus Orbiter: 11 years of data.]" Results published on May 1, 1990.
*[https://web.archive.org/web/20140326001252/http://solarsystem.nasa.gov/multimedia/display.cfm?Category=Spacecraft&IM_ID=16510 Art for the mission]

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[[Category:Missions to Venus]]
[[Category:Pioneer program]]
[[Category:1978 in spaceflight]]
[[Category:Spacecraft launched in 1978]]