Magellan was the first spacecraft to map the surface of Venus globally with radar.
NASA launched Magellan from the Space Shuttle Atlantis on 4 May 1989, and the spacecraft reached Venus in August 1990. Thick clouds permanently hide the planet’s surface from ordinary cameras, so Magellan used synthetic-aperture radar to image the terrain and radar altimetry to measure elevations.
During its mission, Magellan mapped about 98 percent of Venus’s surface at a resolution far better than earlier observations. The data revealed extensive volcanic plains, thousands of volcanic features, large impact craters and unusual circular structures called coronae. The spacecraft also found evidence that Venus has been geologically active in its relatively recent past.
Magellan was not the first spacecraft to visit Venus. Soviet Venera probes achieved major earlier milestones, including the first successful surface images. Magellan’s distinction was global high-resolution radar mapping from orbit.