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 (Crovisier et al, 2002A&A...393.1053C). This service provides access to the Nançay observations of 100+ cometary apparitions between 1982 and 2018. Spectra are provided either as sums of simultaneous acquisitions in different ranges and polarizations (status 2), or averages during short periods (status 3) to increase the signal to noise ratio; status -2 indicates off-target pointing to avoid saturation. Upper limits on OH production rates are provided with value = 0. and error > 0.
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