Cornell H. Mayer, 83, a radio astronomer who measured the thermal radiation from planets and who first calculated the surface temperature of Venus, died Nov. 19 of heart disease at his home in Alexandria.

Mr. Mayer excelled in determining precise measurements from celestial sources. During the 1950s, when radio astronomy was in its infancy and little was known about planet atmospheres or surface temperatures, Mr. Mayer used the Naval Research Laboratory's 50-foot dish antenna to launch his studies.

His 1958 discovery, later confirmed by U.S. and Soviet space probes, that the surface of Venus is hotter than 600 degrees and its atmosphere contains traces of water vapor, contradicted popular perceptions of the time that Venus was habitable.

Mr. Mayer's research also yielded accurate measurements of the surface temperature of Mars and the atmospheric temperature of Jupiter.

He collaborated with Charles H. Townes on experiments to improve the capabilities of detecting planetary thermal radiation. Townes called Mr. Mayer instrumental in the work that resulted in his 1964 Nobel Prize in physics, and he shared a portion of his monetary award with Mr. Mayer.

Mr. Mayer served as head of the Radio Astronomy Branch, Space Science Division, at the Naval Research Lab, where he pursued research activities using massive parabolic dishes to study radiation from the stars and planets and pinpoint optically invisible phenomena in space throughout his 36-year career at the lab. He retired in 1980 after receiving numerous awards, including the Navy Superior Civilian Service Award in 1969. He wrote more than 76 scientific articles and was quoted at length in Isaac Asimov's "The Secret of the Universe."

Mr. Mayer was born in Ossian, Iowa, and graduated from the University of Iowa. He served in the Navy during World War II and, while stationed at the Naval Research Laboratory, participated in the development of the first submarine periscope radar. He received a master's degree in electrical engineering in 1951 from the University of Maryland.

Mr. Mayer was an avid golfer and a member of Belle Haven Country Club.

A son, John Cornell Mayer, died in 1978.

Survivors include his wife of 56 years, Carey Whitehead Mayer, and a daughter, Carolyn Elizabeth Mayer, both of Alexandria.