ARECIBO, P.R. -- Arecibo Observatory, the world's most sensitive and largest radar-radio telescope, is inaugurating an annual lecture series named for William E. Gordon, who was professor of electrical engineering at Cornell University, Ithaca, N.Y., when he conceived of an instrument to study the properties of the ionosphere, the Earth's upper atmosphere.

The inaugural lecture will be given Tuesday, Nov. 12, by Harold Ewen, a retired engineer who was a doctoral candidate at Harvard University in 1951 when he designed and built a horn antenna that would make the first detection of a hydrogen radio emission from interstellar space. Ewen will speak at 3:30 p.m. in the Angel Ramos Foundation Visitor Center at the observatory. The lecture is open to the public without charge.

The Gordon Lecture is endowed by another Arecibo pioneer, engineer Tom Talpey, and his wife, Elizabeth. Talpey was a member of the engineering team led by Gordon that spent three years in Puerto Rico in the early 1960s building Arecibo Observatory, which received its first radio signals in 1963. Since then, the telescope's radar transmitters and sensitive electronic systems for picking up and analyzing weak signals have produced a host of significant scientific results, from the first binary pulsar and confirmation of gravitational radiation to detection of ice on the surface of Mercury.

The observatory is part of the National Astronomy and Ionosphere Center, a national research center operated by Cornell under a cooperative agreement with the National Science Foundation. The telescope is used by scientists from across the United States and around the world.

Ewen made the first detection of atomic hydrogen in interstellar space with the collaboration of the late Harvard physicist Edward Purcell, who was to share the 1952 Nobel Prize in physics for development of nuclear magnetic resonance in measuring magnetic fields in the nuclei of atoms. Purcell obtained a grant of $500 from the American Academy of Arts and Sciences to build the horn antenna. Ewen then designed the antenna and the mixer and receiver, which used a frequency-switching technique to cancel out systematic effects, a novel technique for astronomy at the time. After completing his doctorate, Ewen joined the Harvard faculty and was co-director of the Harvard Radio Astronomy Project from 1952 to 1958. He left Harvard in 1982 to devote himself to his two companies, Ewen Knight Corp. and Ewen Dae Corp., which provided radio equipment for major academic, government and industrial research laboratories. Since 2001 he has been a research professor at the University of Massachusetts. His famous horn antenna is now at the National Radio Astronomy Observatory, Greenbank, W.Va.

For more information about the Gordon Lecture, or to reserve a place, call Edith Alvarez at Arecibo Observatory at (787) 878-2612, extension 210, or e-mail at edith@naic.edu .

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o Arecibo Observatory: http://www.naic.edu/