DOAS enables detection of very weak trace gas 'signatures'

The Differential Optical Absorption Spectroscopy (DOAS) method enables the detection of very weak absorption structures in the spectra of backscattered sun light measured by the satellite instrument. In the centre a spectrum of sunlight scattered back from the earth’s atmosphere is shown. From such spectra the absorption structures of various atmospheric trace gases can be retrieved simultaneously. Graphic from T. Wagner, University of Heidelberg's Institute for Environmental Physics.