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We investigate the physical and chemical conditions in a typical star formingregion, including an unbiased search for new molecules in a spectral regionpreviously unobserved. Due to its proximity, the Orion KL region offers aunique laboratory of molecular astrophysics in a chemically rich, massive starforming region. Several ground-based spectral line surveys have been made, butdue to the absorption by water and oxygen, the terrestrial atmosphere iscompletely opaque at frequencies around 487 and 557 GHz. To cover thesefrequencies we used the Odin satellite to perform a spectral line survey in thefrequency ranges 486-492 GHz and 541-577 GHz, filling the gaps between previousspectral scans. Odin's high main beam efficiency and observations performedoutside the atmosphere make our intensity scale very well determined. Weobserved 280 spectral lines from 38 molecules including isotopologues, and, inaddition, 64 unidentified lines. The beam-averaged emission is dominated by CO,H2O, SO2, SO, 13CO and CH3OH. Species with the largest number of lines areCH3OH, (CH33)2O, SO2, 13CH3OH, CH3CN and NO. Six water lines are detectedincluding the ground state rotational transition o-H2O, its isotopologueso-H218O and o-H217O, the Hot Core tracing p-H2O transition 6(2,4)-7(1,7), andthe 2(0, 2)-1(1,1) transition of HDO. Other lines of special interest are the1_0-0_0 transition of NH3 and its isotopologue 15NH3. Isotopologue abundanceratios of D/H, 12C/13C, 32S/34S, 34S/33S, and 18O/17O are estimated. Thetemperatures, column densities and abundances in the various subregions areestimated, and we find very high gas-phase abundances of H2O, NH3, SO2, SO, NO,and CH3OH. A comparison with the ice inventory of ISO sheds new light on theorigin of the abundant gas-phase molecules.

A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite II. Data analysis