Outdoor Passive Millimeter-Wave Imaging: Phenomenology and Scene Simulation.

A model for scene simulation is presented, which describes quantitatively the recognized phenomenology of passive millimeter-wave (PMW) imaging in land, sea, and air scenarios. The model describes objects in a scene as facets giving them electromagnetic properties from their electrical permittivities. This enables polarimetric effects in scenes to be reproduced. Illumination from the sky and ground is calculated using radiation transport, as are the emissive and absorbing effects of the atmosphere between the objects and the imager. The model includes the effects of image sampling, diffraction effects of finite imager aperture sizes, and system noise. Phenomena in experimentally acquired images in the 94 GHz atmospheric transmission window are quantified from three scenarios. These are a helicopter landing site as viewed by the pilot, a coastal region showing boats, land and buildings viewed from sea level, and an airfield viewed from directly above. These are compared quantitatively to the simulated scenes from these scenarios, finding agreement between the radiation temperatures to within a few degrees kelvin. These discrepancies are accounted for by the uncertainties in the permittivities of materials in the scene. This paper constitutes the partial validation of a scene simulation capability for PMMW imaging in outdoor scenarios. [ABSTRACT FROM PUBLISHER]