PACS image of L1157 of the integrated H₂O emission at 1669 GHz (from Nisini et al. 2010). Offsets are with respect to the L1157-mm source, at coordinates α_J2000 = 20^h39^m062, δ_J2000 =  + 68°02′160. The contours of the SiO 3-2 integrated intensity is superimposed on the water map with a spatial resolution of 18″ (Bachiller et al. 2001). The positions chosen for the HIFI observations (R and B2) are marked by two white circles, which correspond to the largest and the smallest HIFI beam sizes.