Retrieving high-resolution Doppler velocity profiles in 10.6-μ and 2-μm coherent lidars

The performance is considered of some coherent-lidar inverse techniques for retrieving high-resolution Doppler-velocity profiles, with a resolution cell that is far below the pulse length and even of the order of the sampling interval. The speckle noise influence on the retrieved Doppler velocity profiles is investigated as a function of the lidar pulse length, the data sampling interval, the ratio between them, and as a whole, of the lidar radiation wavelength. It is shown that at a constant Doppler-velocity sensitivity the speckle noise error increases with the increase of the pulse length and the decrease of the sampling interval. Moreover, a similarity relation is established consisting in that the level of the error is practically invariable when the ratio of the pulse length to the sampling interval is retained. The results obtained lead to the conclusion that shorter- wavelength lidar radiation should be used not only to retain a good Doppler-velocity sensitivity at shorter pulse lengths, but to retain as well a satisfactorily high accuracy of retrieving the Doppler-velocity profiles, with proportionally shorter range resolution cell.