Thomas D. Jacot, 62, a retired senior physicist at the Johns Hopkins University Applied Physics Laboratory in Laurel, died Friday at University Hospital in Baltimore.

He had been injured that day in the crash of his car and a truck in Beltsville.

A specialist in design of electronic systems in support of Navy ship defenses, Mr. Jacot retired from the laboratory in 1976.

He had joined the labarotory in 1945, during early development of guided missile systems. He served as a research scientist, supervisor and systems engineer for missile guidance development as well as fuze development and modification.

Mr. Jacot had been assigned to guidance system development for TALOS, a supersonic ramjet defense missile, and was coinventor of an electromechanical system that enhanced the TALOS guidance accuracy.

Born in Apple CreeK, Ohio, he was a graduate of the College of Wooster in Ohio and received a master's degree in physics from the University of Akron in 1942.

He served with the Army Signal Corps in 1942 and 1943, and then went to work as a research assistant in metallurgy for the University of Chicago. While there he worked under the Italian nuclear pioneer physicist Enrico Fermi, assisting in the development of the first nuclear reactors.

He was a technologist in physics of the E.I. Dupont Corp. in Richland, Wash., in 1944 and 1945.

He is survived by his wife, Bertha, of the home in Spencerville, Md.; three daughters, Susan, of Baltimore, Ruth, of Sidney, Ohio, and ALice, of Wooster, Ohio, and three sisters, Mabel Tucker and Ella Manson, both of Apple Creek, and Linnet Glasener, of Vandalia, Ohio.