 In 1962 he joined the Smithsonian Astrophysical Observatory and the Harvard College Observatory.There he started a program in gamma-ray astronomy using balloon-borne and ground-based detectors, and the construction of the 10-meter optical reflector at the F. L. Whipple Observatory, Arizona, for the search of ultra-high-energy cosmic gamma-rays.In 1984 Fazio was selected as Principal Investigator for the Infrared Array Camera (IRAC) experiment on the Spitzer Space Telescope (NASA).