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12 December 2006 Estimation of signal and noise for a differential absorption lidar in the mid-infrared band
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The strength of backscattered signals for a Differential Absorption Lidar (DIAL) system operating in the mid infrared band is estimated for the cases of (i) back scattering from topographic targets and (ii) Mie scattering from the aerosols. The estimation is based on the following input parameters : (a) the energy of the lidar transmitted pulses is 20 mJ with pulse duration of 10 nanoseconds and (b) the receiver system consists of a telescope with 500 mm aperture with a field of view of 0.33 mrad. The inherent noise of the detector, background noise due to solar radiation and the noise due to thermal radiation from the objects within the field of view of the receiver, are separately estimated to obtain the total noise in the detection setup. For the case of topographic targets, the reflectivity is taken as 10%. It is shown that atmospheric trace gases like methane with (path integrated) concentration upto 0.5 ppm-km, can be detected without difficulty upto ranges of 5 km. For the Mie scattering from the aerosols, typical meteorological visibility of 10 km is assumed. The case for methane detection is studied. It is shown that during day time, range resolved measurements of trace chemicals can made upto 3 km range, which can be extended to 5 km during night time.
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A. T. Reghunath, Naveen Kumar Verma, and Yogesh Kumar "Estimation of signal and noise for a differential absorption lidar in the mid-infrared band", Proc. SPIE 6409, Lidar Remote Sensing for Environmental Monitoring VII, 64090F (12 December 2006);

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