John A. O'Keefe (1916–2000)



John A. O'Keefe, a pioneer of the Space Age and the man whom Eugene Shoemaker called “the godfather of astrogeology” died September 8 of complications due to liver cancer. He was a Fellow of the AGU.

O'Keefe's best-known scientific achievement was the 1959 discovery of the third harmonic of the Earth's gravitational field, derived from tracking the Vanguard 1 satellite. O'Keefe, together with coauthors Ann Eckels (now Bailey) and Ken Squires (now deceased), analyzed the data at the newly formed NASA Goddard Space Flight Center and concluded that “The third zonal harmonic modifies the geoid toward the shape of a pear,” with an amplitude of 15 meters. This careful statement was headlined as “the pear-shaped earth.” The first discoveries from satellite tracking had already been made by British scientists, who found a new value for the flattening of the Earth from Sputnik 2. However, the third harmonic was the first geodetic result from an American satellite, and its discovery attracted worldwide attention.