Born in 1933 but developed only after the Second World War, radio astronomy involves the study of natural radio waves emitted by celestial objects. In France, the first group of radio-astronomers was established in 1946 at the École normale supérieure around Jean-François Denisse (1915-2014). He soon found the situation too limited, and was invited by André Danjon to join the Observatory. Thus was created an observation unit at Nançay, far from industrial noise. The first instrument created at the station, in 1956, was the radio-heliograph, a large interferometer for solar observations that is still in use following numerous upgrades.

caption : Radio-heliograph - credits : Observatoire de Paris