On the use of Thin Plastic Films as Gas-Phase Analog Targets

Acquiring ground-truth data of gaseous effluent releases concomitant with the collection of remotely sensed hyperspectral imagery (HSI) is a difficult task. Precise ground-truth information is required for algorithm development and testing. Imprecise and/or uncertain truth data impede the development and refinement of information-extraction tools and techniques for gaseous effluents remote sensing. Except for a small number of well-instrumented points in space (usually including plume exit apertures), the true three-dimensional physical and chemical structure of gas plumes is generally unknown. Further compounding this uncertainty are the spatial sampling characteristics of the remote sensing system. It is extremely difficult to assign true gas-effluent quantity to the individual plume-containing pixels imaged by HSI sensors. In an attempt to generate well-truthed data, thin plastic films were assessed as gas-phase analog targets. With thin films, material location, abundance, temperature, and subpixel distributions (for mixtures) can be well known, easily measured, and controlled. Large polyethylene (PE) thin-film panels (`plastic plumes´) were thus deployed during HSI data collection experiments in 2003 and 2005 at which longwave infrared (LWIR) airborne HSI data were acquired. The polyethylene films yielded spectral signatures similar to those of gases; plastic plumes are viable analogs for gaseous effluents. The theoretical background supporting the use of plastic plumes as gas analogs is discussed as are the results of the analysis of the LWIR HSI airborne and ground-truth data.