We consider the design of a system combining computed tomography and Fourier Transform Infrared spectroscopy (CT/FTIR) to detect and map the concentration of multi-contaminant gas plumes in ambient air over a 100 m square area. Several factors affecting the accuracy of the reconstructed map and the detection limits that can be achieved in the field are discussed. The estimated cost and capabilities of the system are compared with those of a more conventional gas monitoring system that might operate over a similar spatial extent. The paper includes a description of a proposed system that is designed to produce a map of multiple gaseous contaminants with a resolution of 12m x 12 m in a time of approximately 10 minutes by sequentially measuring the contaminant concentrations along 48 intersecting beam paths and then reconstructing the map using a CT algorithm adapted to detect Gaussian plumes. The optical elements consist of an FTIR mounted on a steerable telescope platform, a second remote steerable mirror platform, and 32 fixed retro-reflectors.
