As a physicist, Dr. Butler worked at the California Institute of Technology Jet Propulsion Laboratory (JPL) from 1957 to 1960 during the pioneering days of the U.S. space program. He was on the science and tracking team for the first U.S. satellites including Explorer I, and tracked the Soviet Sputnik satellites. The position gave him the opportunity to work with and take courses from such notables as Richard Feynman and Harold Urey. This photo shows Dr. Butler at left, at JPL about 1958. The object in the picture is an analog computer designed to triangulate the altitude of Explorer I and other satellites based on ground/radio observations.