The Odin satellite , launched in Feb. 2001 , is equipped with a 1.1-m submillimetre telescope .
Odin was used to observe the 557 GHz line of water with high spectral resolution in 12 comets between 2001 and 2005 .
Line shapes and spatial mapping provide information on the anisotropy of the outgassing and constraints on water excitation , enabling accurate measurements of the water production rate .
Five comets were regularly observed over periods of more than one month to monitor the variation of their water outgassing rate with heliocentric distance .
Observing campaigns have been generally coordinated with ground-based observations of molecular lines at Nançay , CSO or IRAM 30-m telescopes to obtain molecular abundances relative to water .

Thanks to Odin ’ s frequency coverage , it was also possible to detect the H _ { 2 } ^ { 18 } O 548 GHz line , first in comet 153P/Ikeya-Zhang in April 2002 ( Lecacheux et al .
( 2003 ) ) and then in comets C/2002 T7 ( LINEAR ) , C/2001 Q4 ( NEAT ) and C/2004 Q2 ( Machholz ) .
The ^ { 16 } O/ ^ { 18 } O isotopic ratio ( \approx 450 ) is consistent with the terrestrial value .
Ammonia has been searched for in three comets through its J _ { K } = 1 _ { 0 } -0 _ { 0 } line at 572 GHz and was tentatively detected in C/2001 Q4 and C/2002 T7 .
The derived abundances of NH _ { 3 } relative to water are 0.5 % and 0.3 % , respectively , similar to values obtained in other comets with different techniques .