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Pioneer Venus 1
Pioneer Venus 1 Mission to Venus
Pioneer Venus 1:
Nation: U.S. (60)
Objective(s): Venus orbit
Spacecraft: Pioneer Venus Orbiter
Spacecraft Mass: 582 kg
Mission Design and Management: NASA ARC
Launch Vehicle: Atlas-Centaur (AC-50 / Atlas no. 5030D)
Launch Date and Time: May 20 1978 / 13:13:00 UT
Launch Site: ETR / launch complex 36A

Scientific Instruments:
1) charged-particle retarding potential analyzer
2) charged-particle mass spectrometer
3) thermal electron temperature Langmuir probe
4) neutral-particle mass spectrometer
5) cloud photopolarimeter/imaging system
6) temperature sounding infrared radiometer
7) magnetic field fluxgate magnetometer
8) solar wind plasma analyzer
9) surface radar mapper
10) electric field experiment
11) transient gamma-ray burst experiment
12) gas and plasma environment experiment
13) radio occultation experiment
14) atmospheric and solar corona turbulence experiment
15) drag measurements experiment
16) internal density distribution experiment
17) celestial mechanics experiment

Results: The Pioneer Venus project comprised two spacecraft to explore the atmosphere and surface of Venus. Both spacecraft used a basic cylindrical bus.

Pioneer Venus 1, the orbiter, was designed to spend an extended period in orbit around Venus mapping the surface using a radar package.

The orbiter entered an elliptical orbit around Venus on 4 December 1978 after a 6.5-month journey. The initial orbital period was 23.4 hours, which was altered within two orbits to the desired 24 hours -- a maneuver that would allow the orbit's high and low points (about 150 kilometers) to occur at the same time each Earth day. Data from the radar mapper allowed scientists to produce a topographical map of most of the Venusian surface between 73° north and 63° south latitude at a resolution of 75 kilometers. The data indicated that Venus was much smoother and more spherical than Earth.

The orbiter identified the highest point on Venus as Maxwell Montes, which rises 10.8 kilometers above the mean surface.

Infrared observations revealed a clearing in the planet's atmosphere over the north pole. In addition, ultraviolet light photos showed dark markings that covered the clouds in the visible hemisphere. Cameras also detected almost continuous lightning activity in the atmosphere.

The spacecraft confirmed that Venus has little, if any, magnetic field.

Although the mapping radar was switched off on 19 March 1981, it was reactivated again in 1991, thirteen years after launch, to explore the previously inaccessible southern portions of the planet.

In May 1992, Pioneer Venus 1 began the final phase of its mission, maintaining its periapsis between 150 and 250 kilometers until propellant depletion. The last transmission was received at 19:22 UT on 8 October 1992, as its decaying orbit no longer permitted communications. The spacecraft burned in the atmosphere soon after, ending a successful fourteen-year mission that was planned to last only eight months.

Editor's Note: This mission profile was originally published in Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, by Asif A. Siddiqi, NASA Monographs in Aerospace History No. 24
Key Dates Links
End of Venus Mission
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Last Updated: 06.01.05