Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2016, Vol. 13, No. 3, pp. 198-206
Backscatter nephelometer using a rectangular fragment of the laser pulse
G.P. Arumov
1 , A.V. Bukharin
1 , A.V. Turin
1 1 Space Research Institute RAS, Moscow, Russia
Accepted: 20.05.2016
DOI: 10.21046/2070-7401-2016-13-3-198-206
A coaxial sensing scheme as a basis for of a pulse lidar and nephelometer is presented. In an ideal sensing scheme the angular dimensions of the beam and the field of view are equal for any distance. The nephelometer mode uses a fragment of a rectangular laser pulse. Registration time of counts for the receiver (gate) is equal to the duration of the laser pulse. Dependence of the ratio of return signal in nephelometer mode to the full backscatter signal for lidar mode is linearly dependent on the distance. This makes it possible to determine the depth sensing in the scattering medium. The effectiveness of the use of laser light in the mode of nephelometer is significantly higher than for pulsed lidar. This enables to choose almost safe-eye laser for remote sensing atmosphere from of several hundred meters to several kilometers. Calibration using the standard scattering surface can be made at distances comparable to the length of the near zone of the lidar with minimal use of attenuators. Optimal value for the extinction coefficient αopt can be selected in terms of the laser pulse duration τ as the αopt=2/cτ, where c – speed of light. Registration in the main gate of photon counts from the previous laser pulses was simulated. It is shown that contribution to the backscatter signal from the previous laser pulses is less than 20% of the backscatter signal for the main laser pulse.
Keywords: one-position scheme, coaxial scheme, remote sensing, backscatter coefficient, extinction coefficient, laser diode, geometrical form factor, nephelometer, lidar, scattering, calibration, attenuator
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