Laser Sensing of a Subsurface Oceanic Layer. II. Polarization Characteristics of Signals.

In Part I of this paper we calculated depth profiles and polarization characteristics of airborne lidar return signals by the Monte Carlo method. Here we calculate the polarization characteristics of lidar return signals for different types of water. We demonstrate the feasibility of polarization lidar application to the detection of underwater inhomogeneities of different origins.

Laser sensing of a subsurface oceanic layer. I. Effect of the atmosphere and wind-driven sea waves.

Depth profiles and polarization characteristics of airborne lidar return signals have been calculated by the Monte Carlo method. We analyze some peculiarities of depth profiles of lidar return signals for a rough air-water interface. The distorting effect of the atmosphere on the lidar return signal structure is evaluated as a function of the geometry of the observations.

Influence of the air-water interface on hydrosol lidar operation.

The results of seawater sensing by use of an airborne lidar with a changeable field of view (FOV) are presented, together with the results of numerical simulation of lidar operation by the Monte Carlo method. It is demonstrated that multiple scattering and wind-driven sea waves have opposite effects on the measured attenuation coefficient. At small FOVs the wind-driven sea waves cause the lidar signal decay rate to increase compared with the size of the plane surface and hence result in an overestimation of the retrieved attenuation coefficient.

Polarization structure of lidar signals reflected from ice crystal clouds.

Polarization characteristics of signals of a monostatic lidar intended for sensing of homogeneous ice crystal clouds are calculated by the Monte Carlo method. Clouds are modeled as monodisperse ensembles of randomly oriented hexagonal ice crystals. The polarization state of multiply scattered lidar signal components is analyzed for different scattering orders depending on the crystal shapes and sizes as well as on the optical and geometrical conditions of observation.

Expanding the dynamic range of a lidar receiver by the method of dynode-signal collection.

A method of lidar data collection by simultaneous registration of signals from the anode and several dynodes of the photomultiplier is suggested. The dynamic range of the receiver has been extended as many as 5 orders of magnitude in the case of cloud sensing. The stable operation under strong background illumination is possible without losses in fine signal structure.

Numerical evaluation of the possibilities of remote laser sensing of fish schools.

The operation of an airborne lidar intended for the detection of fish schools is numerically simulated by the Monte Carlo method. The calculations are performed for schools located at small depths in order to study the regularities in the shaping of the lidar return accurately. Three models of the phase function of scattering of laser radiation in sea water are used.