HIFI spectra of comet C/2009 P1 (Garradd) observed on 6 October 2011 with the HRS. HDO (509 GHz), H₂O (557 GHz), and  (548 GHz) 1₁₀–1₀₁ spectra are the average of single-point measurements. The spectrum of the H₂O 2₀₂–1₁₁ line at 988 GHz is extracted from the map, by averaging data at offsets  <10′′ from the peak. The velocity scale is given with respect to the comet rest frame. Synthetic line profiles obtained with 30% extended production (see text) are shown by red dotted lines. Gas acceleration (velocity increasing from 0.48 km s^-1 to 0.58 km s^-1 from r = 10⁴ km to 10⁵ km) is considered to fit more closely the wings of the profiles (Combi et al. 2004).