Marcel Nicolet (1912-1996) was a Belgian aeronomist and geophysicist, born in Basse-Bodeux, and one of the founders of upper-atmosphere research. A doctor of astrophysics from the University of Liège (1937), he founded and directed the Belgian Institute for Space Aeronomy in 1964 and taught at the University of Brussels. As secretary-general of the International Geophysical Year (1957-1958), he played a major role in coordinating that worldwide scientific effort. His work on the composition and structure of the ionosphere earned him numerous international honours (Bowie Medal, 1984); King Baudouin raised him to the rank of baron in 1987.