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Dr. Alan Hildreth Barrett, Professor Emeritus of Physics at the Massachusetts Institute of Technology, died on July 3, 1991, in Denver, Colorado, of cancer.
Professor Barrett was widely known for his scientific contributions to the field of radio astronomy and to the spectroscopic study of the interstellar medium. In addition, he applied the methods of radio astronomy to the study of the Earth's atmosphere and to noninvasive measurements of the human body. Throughout his career he was an active contributor to NASA and NSF committee activities and in 1985 he served as the chairman of the "Barrett Committee" that formulated the future NSF program for millimeter-wave astronomy.
In October, 1963, Professor Barrett and his associates at MIT became the first to detect and measure the presence of hydroxyl (OH) radicals in interstellar space. This discovery was the first detection of molecular line radiation in the radio spectrum, and marked a major milestone in radio astronomy, opening the way for the development of the new field of research on molecules in space. The radio telescope used to make the observations was the 84-foot Millstone Hill instrument, operated by MIT's Lincoln Laboratory.
Following his work on the discovery of the OH radical, he discovered that the polarization and radiation properties of the lines indicated the existence of naturally occurring masers on a cosmic scale. He participated in the first very-long-baseline interferometry measurements of the OH radiation which confirmed the maser hypothesis. For this work he shared in the Rumford Prize of the American Academy of Arts and Sciences in 1971. He continued his research on the molecular properties of the interstellar medium throughout his career. He was awarded a Guggenheim Fellowship in 1977-78 to pursue his studies abroad, and was a von Humboldt fellow in 1987. In 1990, he was designated the Jansky lecturer at the NRAO.
Professor Barrett also was the first to recognize that the extremely high temperature of Venus could be understood if Venus had an extraordinarily thick atmosphere of carbon dioxide. He subsequently was the co-designer of microwave detection equipment carried to Venus aboard the Mariner I and II vehicles and used to observe microwave emissions from that planet in 1960-63.
He also applied radio astronomy techniques to study the characteristics of the Earth's atmosphere, looking down from high altitude balloons, preparing the way for the Nimbus series of meteorological satellites. During his tenure at MIT he supervised the Ph.D. theses of 19 students, all of whom have gone on to prominent positions in scientific research. He was a fellow of the American Academy of Arts and Sciences, and has served as an advisor and consultant to NASA, the National Science Foundation, the National Institute of Health, the National Radio Astronomy Observatory, and the National Astronomy and Ionosphere Center. He was a member of the American Astronomical Society, the International Scientific Radio Union, and the International Astronomical Union.
Professor Barrett was born June 7, 1927, in Springfield, Massachusetts, graduated from the Technical High School in Springfield in 1944, and served in the US Navy during World War II. He received the bachelor of science degree in electrical engineering from Purdue University, West Lafayette, Indiana, in 1950; and the doctor of philosophy degree in physics from Columbia, in 1956, under the supervision of a Nobel laureate, Charles Townes. At Columbia University he pioneered the measurements of the microwave spectra of diatomic molecules at high temperatures.
From 1956 to 1957, Dr. Barrett was a postdoctoral fellow at the US Naval Research Laboratory, Washington, DC, where he concentrated on radio astronomy experiments and techniques.
He served as a research associate and instructor in the Department of Astronomy at the University of Michigan, Ann Arbor, Michigan, from 1957-1961. While at Michigan, Dr. Barrett carried out an extensive theoretical study of the microwave radiation from the atmosphere of Venus. It was this study that led to his being invited to participate as an experimenter in the series of Mariner Venus fly-by space probes.
Dr. Barrett joined the faculty of MIT in 1961 as an associate professor of electrical engineering. He was appointed professor of electrical engineering in 1965, becoming a professor of physics in 1967. He carried out his research in association with the Research Laboratory of Electronics.
He leaves his wife, the former Virginia McCulloch, and two children, Richard and Bonnie, both of Denver, Colorado, and a brother, Raymond, of Santa Barbara, California.
Obituary written by: Bernard F. Burke (MIT)
BAAS Citation: BAAS, 1991, 23, 1489
SAO/NASA ADS Bibcode: 1991BAAS...23.1489B