Arecibo Observatory

World's largest single-dish radio telescope, at Arecibo, Puerto Rico, located in a natural circular depression. The rotation of the Earth causes it to scan the sky once each day. The band of sky that can be observed is 39 degrees in diameter. Measuring 305 m/1,000 ft in diameter, the telescope has been used both for radar work on the planets and for conventional radio astronomy.

Arecibo Observatory is operated by the National Astronomy and Ionosphere Center of Cornell University, Ithaca, New York, and the National Science Foundation. In 1996 it received a US$25 million upgrade and the sensitivity of the disc was increased tenfold. Another upgrade in 1997 added a new receiver, SERENDIP-IV, capable of monitoring 168 million radio channels.