Thomas A. Potemra, supervisor of the Space Physics Group at Johns Hopkins University's Applied Physics Laboratory (APL) in Laurel, Maryland, passed away Friday, April 3, 1998, following extended hospitalization after a heart operation. Tom Potemra had been a physicist in APL's Research Center and Space Department since 1965, specializing in the science and history of the Earth's magnetic field. He led a large group of space scientists, published over 200 scientific papers, and directed many spacecraft experiments. He was deeply involved in defining and implementing major scientific missions for the nation's space program.