Odin is a 250 kg class satellite built in co-operation between Sweden, Canada, France, and Finland and launched in February 2001. It carries two instruments: a 4-band sub-millimetre radiometer used for both astronomy and atmospheric science and an optical spectrometer and infrared imaging system for purely atmospheric observations. As part of the joint mission Odin will observe the atmospheric limb for 50% of the observation time producing profiles of many species of interest in the middle atmosphere with a vertical resolution of 1–2 km. These species include, among others, ozone, nitrogen dioxide, chlorine monoxide, nitric acid, water vapour, and nitrous oxide. An overview of the mission and the planned measurements is given. PACS Nos.: 42.68Mj, 94.10Dy, 95.55Fw