The swedish-led Odin satellite was launched in February 2001, in a time-shared observation program between astronomy and aeronomy, with a payload consisting in two instruments : a Optical Spectrograph and Infra-Red Imaging System (OSIRIS), and a Sub-Millemeter Radiometer (SMR). Since the launch, the SMR instrument has been measuring thermal emission from atmospheric trace constituents of interest in both dynamical transport and stratospheric chemistry, using the limb-sounding technique between 480 and 580 GHz, over a maximum altitude range covering the middle atmosphere (stratosphere-mesosphere) and higher.

Main target species are O3, species related to the O3 destruction cycles like ClO, and H2O and its isotopes. However, preliminary work demonstrated the possibility to retrieve vertical profiles of other species, showing only weak emission lines in the microwave domain of the spectrum. A few days of measurements were obtained for an especially interesting pre-defined band around 576.5 GHz, including a strong CO line, and weak lines from H2CO, ClO and O3 isotopes. Being observed by one of the SMR's four radiometer which is subject to serious instrumental problems, correction for an important frequency shift has to be performed prior to any data analysis.

The re-writing of data files with corrected Local Oscillator frequencies is currently ongoing. Here, the methodology of the frequency correction is briefly explained. Formaldehyde line detection by zonal averaging, and hopefully also the first vertical profiles of carbon monoxide (576.268 GHz) and ozone (576.515 GHz) are presented.