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Feasibility Study for the Mini-Frequency Agile Laser (MFAL) LIDAR System
Final rept. Mar 1994-Jul 1996
HUGHES AIRCRAFT CO EL SEGUNDO CA
Pagination or Media Count:
Direct and coherent detection LIDAR systems were analyzed for DISC and DIAL detection of stack and pollutant chemicals. Tradeoffs included output energies of 60 and 120 ml, powers of 2 and 10 W, and several values of telescope diameter, atmospheric attenuation, and backscatter coefficient. Longer ranges were found with coherent systems. Extrapolation from field data showed that direct detection of stack emissions could he effective up to 5 km. Based on prior laser development and field experience, a conceptual design for a man-portable, direct detection sensor gave a total weight of 33 lb with a length of 15 in., height of 12 in., and width of 6 in. Development of the conceptual design would require low risk application of standard engineering practices. Algorithms were formulated for application to the multi-wavelength data typical of a MiniFAL sensor to circumvent the limitations of the conventional ratio method using two closely spaced wavelengths. The algorithms used the likelihood ratio test methodology of multivariate statistical inference theory and were successfully applied to synthetic and field data. Wavelengths for most of the selected chemicals were identified and by using wavelength shifting in crystals through nonlinear effects, all remaining chemicals of interest could be detected.
APPROVED FOR PUBLIC RELEASE