H₂O 1₁₀−1₀₁ line observed in comet 29P in 2010 with the HIFI instrument of Herschel. The UT date of the observation is indicated in the upper right corner. The velocity scale is in the comet rest frame. The spectra, acquired with the HRS, have been smoothed to a spectral resolution of 129 m s⁻¹, except for the bottom spectrum which shows the average of the spectra obtained on 19 April and 11 May at a spectral resolution of 67 m s⁻¹.