Pioneer Venus 1:
Goals: The Pioneer Venus project called for two spacecraft to explore the atmosphere and surface of Venus. Pioneer Venus 1 was designed to make a radar map of Venus's surface during an eight month mission. Its twin, Pioneer Venus 2, also carried atmospheric probes.

Accomplishments: During a 14-year orbit of Venus, Pioneer Venus 1 used radar to map the surface at a resolution of 75 km (47 miles). It found the planet to be generally smoother than Earth, though with a mountain higher than Mt. Everest and a chasm deeper than the Grand Canyon. The orbiter also found Venus to be more spherical than Earth, consistent with the planet's much slower rotation rate (one Venus day equals 243 Earth days). It confirmed that Venus has little, if any, magnetic field and found the clouds to consist mainly of sulfuric acid. Measurements of this chemical's decline in the atmosphere over the course of the mission suggested that the spacecraft arrived soon after a large volcanic eruption, which may also account for the prodigious lightning it observed.

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20 May 1978:  Launch 4 Feb 1986:  End of Comet Mission 8 Oct 1992:  End of Venus Mission Status:  Successful		Solar System Bodies: Venus Pioneer Venus 1 Multimedia Gallery NSSDC Master Catalog: Pioneer Venus 1 NSSDC Pioneer Venus Project Page
Pioneer Venus 1 was the first spacecraft to map the surface of Venus (right). Though it found Venus to be generally smoother than Earth, it found a mountain 2 km (about one mile) higher than Mt. Everest and a canyon about 1.1 km (about 2/3 of a mile) deeper than the Grand Canyon. The International Astronomical Union named almost all of the features discovered by Pioneer Venus 1 and subsequent missions after historical or mythological women.