NATIONAL ASTRONOMY AND IONOSPHERE CENTER . ... The Arecibo Observatory is part of the National Astronomy and Ionosphere Center (NAIC), a national research center operated by SRI International, USRA and UMET, under a cooperative agreement with the National Science Foundation (NSF). ... As the site of the world's largest single-dish radio telescope, the Observatory is recognized as one of the most important national centers for research in radio astronomy, planetary radar and terrestrial aeronomy. ...