His doctoral work at Harvard was the design , construction , testing , and flight of a balloon - borne , low - energy , gamma ray telescope .
Hoffman 's original research interests were in high - energy astrophysics , specifically cosmic gamma ray and x-ray astronomy .
Hoffman 's doctoral work at Harvard was the design , construction , testing , and flight of a balloon - borne , low - energy , gamma ray telescope .
Hoffman 's original research interests were in high - energy astrophysics , specifically cosmic gamma ray and x-ray astronomy .