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5 September 2003 Narrow-band signature propagation through obscuring atmospheres
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Methods are examined for modeling ultra narrow band signature propagation through both natural and optically dense or obscured atmospheres. The impetus for the study comes from the recent exploitation of (ultra)narrow band atomic line filters which have become practical for remote sensing applications and real battlefield sensors. Aside from the obvious advantage of being able to "squeeze" the narrow-band signal through (near) equally narrow-band "windows" of the natural (gaseous) atmoshpere; there are a number of other issues that come into play that are either negligible or irrelevant in the more usual broadband applications but may be important here. For example, another way the technology can be exploited is by selecting the filter wavelength so as to take advantage of the Fraunhofer absorption lines in the solar spectrum, thsu producing an effective "solar blind" sensor and the attendant advantages thereof. In this paper we address both practical issues such as line broadening by various known atmosphere processes, including extinction and scattering by suspended aerosols and adverse weather, as well as some more subtle issues such as the effect of the wavelength shift due to atmospheric refraction and Doppler shifting due to the relative motion of the Earth with respect to the Sun; both of which though admitted small and thus negligible in broadband applications could be important here. Our main technical approach is through simulation using conventional models such as MODTRAN and EOSAEL (battlefield atmospheres), augmented as necessary for the task at hand. Preliminary results based on side-by-side comparisons with conventional broadband technologies (e.g., interference filters, Δλ≈10nm, FWHM) are discussed and shows both advantages and disadvantages of the narrow-band technology.
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Joseph R. Montoya and Robert A. Sutherland "Narrow-band signature propagation through obscuring atmospheres", Proc. SPIE 5075, Targets and Backgrounds IX: Characterization and Representation, (5 September 2003);


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