A roto-vibrational resolved corona model is discussed for the simulation of the Fulcher spectrum in Hydrogen low pressure discharges. The model allows to derive H2 rotational and vibrational temperatures from the analysis of emission spectra in the [600:640] nm range. The model is applied to the analysis of emission spectra collected at the SPIDER negative ion source. Results are presented for different values of the applied power to the plasma, pressure, and for different regions of the plasma, thus providing a characterization of the plasma with respect to the internal temperatures of the molecular component.