  In this letter, a new approach for the retrieval of the vertical column
concentrations of trace gases from hyperspectral satellite observations, is
proposed. The main idea is to perform a linear spectral unmixing by estimating
the abundances of trace gases spectral signatures in each mixed pixel collected
by an imaging spectrometer in the ultraviolet region. To this aim, the sparse
nature of the measurements is brought to light and the compressive sensing
paradigm is applied to estimate the concentrations of the gases' endemembers
given by an a priori wide spectral library, including reference cross sections
measured at different temperatures and pressures at the same time. The proposed
approach has been experimentally assessed using both simulated and real
hyperspectral dataset. Specifically, the experimental analysis relies on the
retrieval of sulfur dioxide during volcanic emissions using data collected by
the TROPOspheric Monitoring Instrument. To validate the procedure, we also
compare the obtained results with the sulfur dioxide total column product based
on the differential optical absorption spectroscopy technique and the retrieved
concentrations estimated using the blind source separation.
