Context :

Aims : We investigate the physical and chemical conditions in a typical star forming region , including an unbiased search for new molecules in a spectral region previously unobserved .

Methods : Due to its proximity , the Orion KL region offers a unique laboratory of molecular astrophysics in a chemically rich , massive star forming region .
Several ground-based spectral line surveys have been made , but due to the absorption by water and oxygen , the terrestrial atmosphere is completely opaque at frequencies around 487 and 557 GHz .
To cover these frequencies we used the Odin satellite to perform a spectral line survey in the frequency ranges 486 – 492 GHz and 541 – 577 GHz , filling the gaps between previous spectral scans .
Odin ’ s high main beam efficiency , \eta _ { \mathrm { mb } } = 0.9 , and observations performed outside the atmosphere make our intensity scale very well determined .

Results : We observed 280 spectral lines from 38 molecules including isotopologues , and , in addition , 64 unidentified lines .
A few U-lines have interesting frequency coincidences such as ND and the anion SH ^ { - } .
The beam-averaged emission is dominated by CO , H _ { 2 } O , SO _ { 2 } , SO , ^ { 13 } CO and CH _ { 3 } OH .
Species with the largest number of lines are CH _ { 3 } OH , ( CH _ { 3 } ) _ { 2 } O , SO _ { 2 } , ^ { 13 } CH _ { 3 } OH , CH _ { 3 } CN and NO .
Six water lines are detected including the ground state rotational transition 1 _ { 1 , 0 } – 1 _ { 0 , 1 } of o -H _ { 2 } O , its isotopologues o -H _ { 2 } ^ { 18 } O and o -H _ { 2 } ^ { 17 } O , the Hot Core tracing p -H _ { 2 } O transition 6 _ { 2 , 4 } – 7 _ { 1 , 7 } , and the 2 _ { 0 , 2 } – 1 _ { 1 , 1 } transition of HDO .
Other lines of special interest are the 1 _ { 0 } – 0 _ { 0 } transition of NH _ { 3 } and its isotopologue ^ { 15 } NH _ { 3 } .
Isotopologue abundance ratios of D/H , ^ { 12 } C/ ^ { 13 } C , ^ { 32 } S/ ^ { 34 } S , ^ { 34 } S/ ^ { 33 } S , and ^ { 18 } O/ ^ { 17 } O are estimated .
The temperatures , column densities and abundances in the various subregions are estimated , and we find very high gas-phase abundances of H _ { 2 } O , NH _ { 3 } , SO _ { 2 } , SO , NO , and CH _ { 3 } OH .
A comparison with the ice inventory of ISO sheds new light on the origin of the abundant gas-phase molecules .

Conclusions :