Denney J. Keys, 54, who had been a senior technical fellow for power systems engineering at NASA, died of cancer Dec. 30 at his home in Mitchellville.

His wife, Mary Ellen Keys, confirmed the death.

Mr. Keys joined NASA in 1990 as a power systems engineer, and he worked there until his death. He received the NASA Medal for Exceptional Service in 2005 and the NASA Exceptional Engineering Achievement Medal in 2011.

Denney Jerome Keys was born in Las Cruces, N.M. He graduated in 1980 from the University of Colorado at Boulder, where he also received a master’s degree in mechanical engineering in 1986.

Survivors include his wife of 30 years, Mary Ellen Hynes “Mimi” Keys of Mitchellville; his mother, Helen M. Keys, of Cinnaminson, N.J.; two sisters; and two brothers.

— Bart Barnes