A method for detecting atmospheric trace gas emissions at a specific target location from an observation platform, the method comprising: a) providing an image gathering device at said platform, said platform overflying said specific target location; b) providing a wide-angle Fabry-Perot interferometer at said platform, said wide-angle Fabry-Perot interferometer being a Fabry-Perot interferometer that simultaneously receives multiple light beams having a range of incidence angles, such that light gathered from said specific target location passes through said interferometer before being received by said image gathering device, said interferometer allowing said atmospheric trace gas emissions for a target area to be measured using light at multiple wavelengths; c) determining, by way of a data processing module, a spectral response of a plurality of pixels on said image gathering device to said light gathered from said specific target location based on a traversal angle for said interferometer; and d) recursively adjusting, by way of said data processing module, parameters of a predetermined model and recursively comparing said spectral response from said image gathering device with results from said model to determine vertical column densities of said atmospheric trace gases at said specific target locations, said vertical column densities being derived from said predetermined model when relevant atmospheric spectroscopy and a full instrument response from devices on said platform are considered; the method further including a step of gathering multiple images of said target area as said platform travels over said specific target location; and wherein step b) includes applying an order-sorting filter to said interferometer, wherein said order-sorting filter is a bandpass filter transmitting a selected spectral range comprising at least two adjacent modes of the Fabry-Perot interferometer, characterized in that the Fabry Perot interferometer is configured such that spectral information at all wavelengths of the selected spectral range is acquired by the Fabry Perot interferometer, so that spectral selection is achieved as a result of the angular wavelength shift and the order sorting filter. a) providing an image gathering device at said platform, said platform overflying said specific target location; b) providing a wide-angle Fabry-Perot interferometer at said platform, said wide-angle Fabry-Perot interferometer being a Fabry-Perot interferometer that simultaneously receives multiple light beams having a range of incidence angles, such that light gathered from said specific target location passes through said interferometer before being received by said image gathering device, said interferometer allowing said atmospheric trace gas emissions for a target area to be measured using light at multiple wavelengths; c) determining, by way of a data processing module, a spectral response of a plurality of pixels on said image gathering device to said light gathered from said specific target location based on a traversal angle for said interferometer; and d) recursively adjusting, by way of said data processing module, parameters of a predetermined model and recursively comparing said spectral response from said image gathering device with results from said model to determine vertical column densities of said atmospheric trace gases at said specific target locations, said vertical column densities being derived from said predetermined model when relevant atmospheric spectroscopy and a full instrument response from devices on said platform are considered; <EOS>