Since 1973, the 18-cm lines of the OH radical have been
systematically observed in a number of comets with the Nançay radio
telescope. This allowed an evaluation of the cometary water production
rates and their evolution with time, as well as a study of several
physical processes: the excitation mechanisms of the OH radio lines,
the expansion of the cometary atmospheres, their anisotropy in
relation with non-gravitational forces, the Zeeman effect in relation
with the cometary magnetic field. The Nançay observations of 53
cometary apparitions between 1982 and 2009 are now organized in this
database.
