Encyclopedia Astronautica
Pioneer 12


American Venus probe. One launch, 1978.05.20, Pioneer Venus Orbiter. Pioneer Venus Orbiter. Part of the Pioneer program Pioneer Venus Orbiter was designed to perform long-term observations of the Venusian atmosphere and surface features.

Data from the Orbiter was correlated with data from its sister vehicle (Pioneer Venus Multiprobe and its atmospheric probes) to relate specific local measurements to the general state of the planet and its environment as observed from orbit. Despite their drastically different roles, the Orbiter and Multiprobe were very similar in design. The use of identical systems (including flight hardware, flight software, and ground test equipment) and incorporation of existing designs from previous missions (including OSO and Intelsat) allowed the mission to meet its objectives at minimum cost.

The spacecraft was spin stabilized at ~15 rpm. Body mounted solar panels provided 312 W and recharged 2 x 7.5 Ah NiCd batteries. A 1.09 m despun dish antenna was used for high rate S-band communication with Earth, with low-gain omni antennas for emergency communication. 4 x 10W TWTAs powered the radar. An X-band transmitter was also incorporated for occultation measurements. Attitude determination was by sun sensors and star sensors. Nutation damping was performed with a partially filled tube of liquid Freon. The hydrazine propellant system used 7 thrusters for attitude control and orbit adjustment. A solid rocket motor providing 18 kN of thrust for Venus orbit insertion. A 4.8 m deployable boom was provided for the magnetometer.

The Pioneer Venus Orbiter carried 17 experiments (with a total mass of 45 kg). Most of the instruments were still operating when the spacecraft entered the atmosphere. They included:

  • Cloud photopolarimeter - measured the vertical distribution of the clouds.
  • Surface radar mapper - mapped planetary topography and surface characteristics.
  • Infrared radiometer - monitored IR emissions from the Venusian atmosphere.
  • Air-glow ultraviolet spectrometer - measured scattered and emitted UV radiation.
  • Neutral mass spectrometer - evaluated the composition of the upper atmosphere.
  • Solar wind plasma analyzer - measured properties of the solar wind.
  • Magnetometer - examined Venus' magnetic field.
  • Electric field detector - studied the solar wind and its interactions with the Venusian atmosphere.
  • Electron temperature probe - examined the thermal properties of Venus' ionosphere.
  • Ion mass spectrometer - measured the ionospheric ion population.
  • Charged particle retarding potential analyzer - Studied ionospheric particles.
  • Two radio science experiments - mapped Venus' gravity field.
  • Radio occultation experiment - helped characterize the atmosphere.
  • Atmospheric drag experiment - upper atmosphere density measurements.
  • Radio science atmospheric and solar wind turbulence experiment.
  • Gamma ray burst detector - monitored gamma ray burst events.

Gross mass: 582 kg (1,283 lb).
Height: 1.20 m (3.90 ft).
First Launch: 1978.05.20.
Number: 1 .

More... - Chronology...


Associated Countries
See also
  • Atlas The Atlas rocket, originally developed as America's first ICBM, was the basis for most early American space exploration and was that country's most successful medium-lift commercial launch vehicle. It launched America's first astronaut into orbit; the first generations of spy satellites; the first lunar orbiters and landers; the first probes to Venus, Mars, Mercury, Jupiter, and Saturn; and was America's most successful commercial launcher of communications satellites. Its innovative stage-and-a-half and 'balloon tank' design provided the best dry-mass fraction of any launch vehicle ever built. It was retired in 2004 after 576 launches in a 47-year career. More...

Associated Launch Vehicles
  • Atlas The Atlas rocket, originally developed as America's first ICBM, was the basis for most early American space exploration and was that country's most successful medium-lift commercial launch vehicle. It launched America's first astronaut into orbit; the first generations of spy satellites; the first lunar orbiters and landers; the first probes to Venus, Mars, Mercury, Jupiter, and Saturn; and was America's most successful commercial launcher of communications satellites. Its innovative stage-and-a-half and 'balloon tank' design provided the best dry-mass fraction of any launch vehicle ever built. It was retired in 2004 after 576 launches in a 47-year career. More...

Associated Manufacturers and Agencies
  • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...
  • NASA Ames American agency overseeing development of rockets and spacecraft. Ames, USA. More...
  • Hughes American manufacturer of rockets, spacecraft, and rocket engines. Hughes Aircraft Co. , USA More...

Associated Programs
  • Pioneer The Jet Propulsion Laboratory Pioneer series were the first US probes sent towards the moon. Later Pioneers explored the heliocentric space environment and were the first spacecraft to reach the outer planets and to escape from the solar system. More...

Bibliography
  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.
  • JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Web Address when accessed: here.
  • Ertel , Ivan D; Morse , Mary Louise; et al, The Apollo Spacecraft Chronology Vol I - IV NASA SP-4009, NASA, 1966-1974. Web Address when accessed: here.
  • Lockheed Martin Coporation, Atlas Family Fact Sheets, September 1998.. Web Address when accessed: here.
  • National Space Science Center Planetary Page, As of 19 February 1999.. Web Address when accessed: here.
  • NASA Report, Pioneering Venus: A Planet Unveiled; The Pioneer Project and the Exploration of the Planet Venus, Web Address when accessed: here.
  • NASA Report, The Pioneer Venus Orbiter: 11 years of data. A laboratory for atmospheres seminar talk, Web Address when accessed: here.

Associated Launch Sites
  • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...
  • Cape Canaveral LC36A Atlas launch complex. Launch site built in 1960 for NASA's Atlas/Centaur development program, and used for launches of that launch vehicle until its retirement. More...

Pioneer 12 Chronology


1973 January 26 - .
  • Ames requested six R4D rocket engines surplus to the Apollo program for Pioneer-Venus - . Nation: USA. Program: Apollo. Spacecraft: Pioneer 12. Ames Research Center requested that six R4D rocket engines designed for use in the Apollo program be transferred from MSC to Ames. Possibly the engines would be suitable for the retro-injection function in the Pioneer Venus series of atmospheric probe and orbiter missions. First launch was planned for early 1977.

1978 May 20 - . 13:13 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC36A. LV Family: Atlas. Launch Vehicle: Atlas Centaur SLV-3D. LV Configuration: SLV-3D Centaur AC-50 / Centaur D-1AR 5030.
  • Pioneer Venus Orbiter - . Payload: Pioneer-Venus 1. Mass: 582 kg (1,283 lb). Nation: USA. Agency: NASA Ames. Program: Pioneer. Class: Venus. Type: Venus probe. Spacecraft: Pioneer 12. Decay Date: 1992-10-22 . USAF Sat Cat: 10911 . COSPAR: 1978-051A. The Pioneer Venus Orbiter was inserted into an elliptical orbit around Venus on December 4, 1978. After entering orbit around Venus in 1978, the spacecraft returned global maps of the planet's clouds, atmosphere and ionosphere, measurements of the atmosphere-solar wind interaction, and radar maps of 93 percent of the planet's surface. Additionally, the vehicle made use of several opportunities to make systematic UV observations of several comets. From Venus orbit insertion to July 1980, periapsis was held between 142 and 253 km (at 17 degrees north latitude) to facilitate radar and ionospheric measurements. The spacecraft was in a 24 hour orbit with an apoapsis of 66,900 km. Thereafter, the periapsis was allowed to rise (to 2290 km at maximum) and then fall, to conserve fuel. In 1991 the Radar Mapper was reactivated to investigate previously inaccessible southern portions of the planet. In May 1992 Pioneer Venus began the final phase of its mission, in which the periapsis was held between 150 and 250 km until the fuel ran out and atmospheric entry destroyed the spacecraft. With a planned primary mission duration of only eight months, the spacecraft remained in operation until October 8, 1992 when it finally burned up in Venus' atmosphere after running out of propellant.

1978 December 4 - .
  • Pioneer Venus 1, Venus Orbit Insertion - . Nation: USA. Spacecraft: Pioneer 12.

1992 October 8 - .
  • Pioneer Venus Burnup In Venus' Atmosphere - . Nation: USA. Spacecraft: Pioneer 12.

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