The unique design of the telescope was based on the efforts of Gordon, beginning in 1958, when he was a professor of engineering at Cornell, to build an instrument that would use radar to study the ionosphere, the third layer of the Earth's atmosphere, and objects in the solar system. Between1948 and 1966, Gordon conceived, supervised the design and construction and directed the early operation of the Arecibo Observatory with its 300-meter (1,000 feet) dish antenna.

The telescope's radar transmitters and sensitive electronic systems for picking up and analyzing weak signals have since produced a host of significant scientific results, from the discovery of the first binary pulsar and confirmation of gravitational radiation to detection of ice on the surface of Mercury.

Gordon will present his talk, "The Arecibo Story," at 4 p.m. at the Angel Ramos Foundation Visitor and Education Center at the observatory.

The National Astronomy and Ionosphere Center at Cornell University, Ithaca, N.Y., manages Arecibo Observatory for the National Science Foundation.

Currently a consultant for Northwest Research Associates on large radar facilities and an adviser to the U.S. Air Force and Navy, Gordon served in the Air Force during World War II and earned a Ph.D. at Cornell University in 1953, eventually joining the faculty and remaining until 1966.

At Rice University from 1966 to 1986 he was professor of space science and electrical engineering. He also served as dean of sciences and engineering, as provost and as vice president. He is now a distinguished professor emeritus.

He is a member of the National Academy of Sciences and the National Academy of Engineering and a fellow of the American Academy of Arts and Sciences, the American Association for the Advancement of Science, the American Geophysical Union and the Institute of Electrical and Electronic Engineers.