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Odin in space. (Credit: SSC)

The Odin satellite – an observatory for sub-millimetre wave spectroscopy – was launched from Svobodny in far-eastern Russia on February 20, 2001. Odin was designed for research in both astronomy (e.g. studies of the star formation process in our Galaxy) and aeronomy (e.g. studies of the depletion of the ozone layer in Earth's atmosphere).

The astronomy part of the mission was successfully concluded in the spring of 2007. Since then the satellite has been used exclusively for studies of the Earth’s atmosphere. The astronomy mission scientist was Åke Hjalmarson at Onsala Space Observatory.

An astronomical highlight of the Odin mission was the first discovery of interstellar molecular oxygen. The observations were made at the frequency 119 GHz towards the rho Ophiuchi A gas cloud. Due to the oxygen in Earth's atmosphere, such observations cannot be made from the ground. Oxygen is a fairly common element in the Universe, and it was expected that oxygen molecules would be abundant in cosmic molecular clouds. But the dected signal was much weaker than expected, corresponding to an amount of oxygen molecules only 5·10–8 of the amount of hydrogen molecules.

The aeronomy mission scientist is Donal Murtagh at the research group Global environmental measurements and modelling at the Division for Microwave and Optical Remote Sensing at the Department of Space, Earth and Environment, Chalmers. The group at Chalmers is the main data processing centre for the sub-mm radiometer instrument providing the atmospheric community with quality assessed data.

Odin was built by the Swedish Space Corporation, on behalf of the Swedish National Space Board and the space agencies of Canada (CSA), Finland (TEKES) and France (CNES). The microwave radiometer system was integrated, tested and optimised by Onsala Space Observatory engineers.