Many discoveries about Venus have been made using Earth-based radio telescopes, which can transmit powerful radar signals and detect the weak echoes reflected from the planet's surface.
Arecibo Observatory, Puerto Rico
At 300 meters (1,000 feet) across, Arecibo is the world's largest radio "dish." Smaller radio telescopes, such as the Goldstone Solar System Radar in California, have also been used to map Venus.
Courtesy of David Parker, Science Photo Library
Global Map of Venus
A 12.6-cm wavelength radar image of Venus collected in 2012 by CEPS scientists using the world's two largest radio telescopes: the Arecibo Observatory in Puerto Rico and the Green Bank Telescope in West Virginia. The dark stripe along the center shows the region where the radar mapping technique cannot obtain a high-resolution image
Courtesy of Bruce Campbell, Smithsonian Institution
Green Bank Telescope (GBT)
The new Robert C. Byrd Green Bank Telescope became operational in August 2000. It has been used in conjunction with Arecibo to produce more detailed Earth-based images of Venus than ever before.