Highlights from the first year of Odin observations

Key Odin operational and instrumental features and highlights from our sub-millimetre and millimetre wave observations of H2O, H2 18O, NH3, 15NH3 and O2 are presented, with some insights into accompanying Odin Letters in this A&A issue. We focus on new results where Odin's high angular resolution, high frequency resolution, large spectrometer bandwidths, high sensitivity or/and frequency tuning capability are crucial: H2O mapping of the Orion KL, W3, DR 21, S 140 regions, and four comets; H2O observations of Galactic Centre sources, of shock enhanced H2O towards the SNR IC 443, and of the candidate infall source IRAS 16293-2422; H2 18O detections in Orion KL and in comet Ikeya-Zhang; sub-mm detections of NH3 in Orion KL (outflow, ambient cloud and bar) and ρ Oph, and very recently, of 15NH3 in Orion KL. Simultaneous sensitive searches for the 119 GHz line of O2 have resulted in very low abundance limits, which are difficult to accommodate in chemical models. We also demonstrate, by means of a quantitative comparison of Orion KL H2O results, that the Odin and SWAS observational data sets are very consistently calibrated.