Comparison between the best-fit model (red points) obtained in G15 from comparisons of a grid of models from the Paris-Durham shock code with observations (black squares) of H₂ (from the Spitzer-IRS telescope) and CO (from the APEX telescope). The target position is the northern shock called SiO-knot in G15 and roughly corresponding to knot A of the current study. Upper panel: H₂ excitation diagram. Middle panel: CO integrated intensity diagram. Lower panel: [O i]  line flux. The newly presented CO (5–4, 9–8, 14–13, 18–17, 20–19, and 22–21) transitions observed with Herschel HIFI and PACS have been added to the previously fitted APEX CO lines in the intensity diagram and are satisfactorily fitted by the model.