Ground-based imaging differential optical absorption spectroscopy of atmospheric gases.

We describe a compact remote-sensing instrument that permits spatially resolved mapping of atmospheric trace gases by passive differential optical absorption spectroscopy (DOAS) and present our first applications of imaging of the nitrogen dioxide contents of the exhaust plumes of two industrial emitters. DOAS permits the identification and quantification of various gases, e.g., NO2, SO2, and CH2O, from their specific narrowband (differential) absorption structures with high selectivity and sensitivity. With scattered sunlight as the light source, DOAS is used with an imaging spectrometer that is simultaneously acquiring spectral information on the incident light in one spatial dimension (column). The second spatial dimension is scanned by a moving mirror.