Platinum silicide, indium antinomide, and mercury cadmium telluride are compared as detector materials for an air-to-ground reconnaissance/targeting sensor using the 3 to 5 micrometer infrared band. The comparison is based on a scaled count rate involving only the detector material quantum efficiency, the reflected and thermal emission from the target and background, and the atmospheric trans- mission--all of which are highly wavelength dependent. Last year, the results of analyzing baseline scenario and seven sensitivity scenarios were presented. In these analyses, only the target was considered in the independent variation of each of the following parameters: target temperature, target reflectivity (emissivity), atmospheric visibility, atmospheric aerosol type, and humidity. This year, in a follow-on effort, several baseline scenarios were constructed to determine relative contrast between the standard target and four backgrounds--vegetation, soil, sand, and snow. Six sensitivity analysis scenarios were constructed in which target and background temperatures are varied from the baseline. In three additional scenarios, the atmospheric humidity and target reflectiv- ity are independently varied from the baseline. Initial studies to explore the benefit of dual band operation within 3 to 5 micrometers have been done.