Magellan:
The Magellan orbiter explored
Venus from a near polar, elliptical
orbit. The spacecraft made detailed
maps of 98 percent of the planet's surface using synthetic aperture radar.
Radar imagery revealed that volcanoes have left their mark on about 85 percent of Venus, with lava plains, lava domes, large shield volcanoes and extremely long lava channels. The rest of the planet's surface is covered with ranges of deformed
mountains.
Magellan also made detailed gravity maps of Venus, determining that the
gravity field is highly correlated with surface topography.
The spacecraft was destroyed when mission controllers commanded it to plunge into the planet's dense atmosphere on Oct. 11, 1994. The purpose of the descent was to get some final data about Venus' atmosphere before the aging spacecraft ran out of power.
Visit the Magellan Website