John A. O'Keefe (astronomer)

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John Aloysius O'Keefe III (October 13, 1916 – September 8, 2000) was an expert in planetary science and astrogeology with the National Aeronautics and Space Administration (NASA) from 1958 to 1995.

He and his co-authors, Ann Eckels and Ken Squires, are credited with the discovery that the Earth had a significant third degree zonal spherical harmonic in its gravitational field using U.S. Vanguard 1 satellite data collected in the late 1950s.^[1][2] The Earth's pear shape as it was known became front-page news and was even the subject of a "Peanuts" cartoon.^[3] For that, he is credited as the "father of space geodesy".^[4]

He was the first to propose the idea of a scanning microscope in 1956 and he is the co-discoverer of the YORP effect (short for Yarkovsky-O’Keefe-Radzievskii-Paddock effect), an effect resulting from sunlight which causes a small celestial body such as an asteroid or meteor to spin up or down.