Montage of our solar system

A quarter-century of exploring the solar system will be marked Monday, Dec. 14, on the 25th anniversary of NASA's first planetary mission.

Mariner 2, built at the Jet Propulsion Laboratory, executed flyby of Venus on Dec. 14, 1962. The mission was the first time spacecraft visited another planet.

Since then, more than dozen U.S. spacecraft have explored the planets from Mercury to Uranus, with Neptune to be added during Voyager 2's encounter in 1989. In addition, more than 20 missions to planets -- and, more recently, to Comet Halley -- have been launched in the past 25 years by the Soviet Union, Japan and the European Space Agency.

Mariner 2, launched on August 27, 1962, was one of two early spacecraft built for NASA by JPL to fly by Venus. Its twin craft, Mariner 1, was destroyed when faulty guidance software took its booster off-course during launch on July 22, 1962.

The 447-pound Mariner 2 flew by Venus at distance of 21,600 miles after traveling 180 million miles over 109 days. During its flight it became the first spacecraft to execute trajectory correction maneuver, in which thrusters are fired to correct spacecraft's course.

Among findings from its six science experiments, Mariner 2 confirmed then-theory that Venus was very hot planet with surface temperature of about 800 degrees F. on both its light and dark sides. The spacecraft also relayed data on radiation conditions in the inner solar system.

Later highlights of NASA's planetary program have included Mariner 5 to Venus; Mariners 4, 6, 7, 8 and 9 to Mars; Mariner 10 to Venus and Mercury; Pioneers 10 and 11 to Jupiter and Saturn; Vikings 1 and 2 to Mars; Voyagers 1 and 2 to Jupiter, Saturn, Uranus and Neptune; and Pioneers 12 and 13 to Venus.

NASA's next mission to Venus will be Magellan, scheduled for launch from the Space Shuttle Atlantis on April 27, 1989. The JPL-managed spacecraft will relay high- resolution maps of Venus using synthetic-aperture radar to pierce the planet's thick cloud cover.

Other JPL projects scheduled for launch include Galileo to Jupiter, Oct. 8, 1989; Ulysses, joint mission with the European Space Agency to study the Sun, Oct. 5, 1990; and Mars Observer, August 1992.

NASA/JPL scientists will also collaborate with their Soviet counterparts by tracking and contributing an experiment to the USSR's Phobos mission, which will be launched to study Mars and its moon Phobos in 1988.

JPL planetary projects are funded by NASA's Office of Space Science and Applications.

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