The site of what was formerly the world’s largest radio astronomy dish, 305 m in diameter, opened in 1963 and upgraded in 1974 when the original wire-mesh surface was replaced by solid panels. The observatory is situated 12 km south of Arecibo, Puerto Rico, and is part of the National Astronomy and Ionosphere Center (NAIC), a US national research centre jointly managed by SRI International, the Universities Space Research Association, and the Universidad Metropolitana of San Juan, Puerto Rico. The dish was suspended in a natural hollow in the ground, and scanned a strip of sky overhead as the Earth rotated. Radio sources could be tracked within 20° of the zenith by using movable feeds suspended above the stationary reflector, giving coverage in declination from about 38° north to 1° south. It operated at wavelengths from 6 m to 3 cm. The Arecibo dish was used for atmospheric studies as well as astronomy. It was closed in 2020 November after structural failures rendered it unusable.

http://www.naic.edu/ Official observatory website.