[Doc Ewen looks into the horn antenna, 1950]
Image courtesy of Doc Ewen


Harvard Cyclotron: 1948-1951

Detection of HI Line: 1951

Harvard 24ft and 60ft and NRAO founding: 1952-1956

1950s and 1960s: Two Roads that Crossed

Microwave & Millimeter Wave Applications in the 1970s and 1980s

Mm Wave Radiometry in the 1990s

May 2001 visit to NRAO Green Bank



[Doc Ewen and horn antenna, 2001]
Image courtesy of Doc Ewen

Doc Ewen: The Horn, HI, and Other Events in US Radio Astronomy

by Doc Ewen, © 2003

Slide 28: Detecting the Interstellar Hydrogen Line, 1951

[Letter from Pawsey to Purcell]

Letter from Joseph Pawsey to Ed Purcell, April 20, 1951. Frank Kerr, teaching at Harvard while on leave from CSIRO Division of Radiophysics, had written to Pawsey of the detection. At Purcell's suggestion, I went to the Harvard Observatory, in mid April, to meet and talk to Van de Hulst for the first time, and to tell him about the discovery. Ed told me that Van de Hulst was teaching a course at Harvard during the spring term. It was the same course that he taught at Leiden, during the prior fall term. When I met with Van de Hulst at the Observatory he called Oort, and I talked with Oort for nearly an hour describing the switch frequency technique. This was the first time that we learned the Dutch had been searching for the line for several years. Had we known, we would not have tried. [Photo courtesy of Doc Ewen]

Slides 29-30
Modified on Monday, 06-Sep-2004 14:18:35 EDT by Ellen Bouton