Power transmission coefficients absorption

The ratio of to of Eq. (35-34) gives the transmission coefficient. We express in terms of the ray invariant using the relationship in Table 36-1, page 695, and nj, in terms of the power absorption coefficient a., of Eq. (6-19). Hence... 

Where Pq(A) is the transmitted power, T(k) is the transmission of the clean air from the Lidar to target and back to the Lidar, li(A) is the reflection-coefficient of the target, D is the solid angle of the Lidar telescope, absorption coefficient of the investigated gas, P(A) is the received power. 

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