Yurij I. Kopilevich

Applicability of lidar remote sensing methods for vertical structure investigation of ocean optical properties distribution

The results of theoretical study of the problem of detectability of vertical profiles of hydro- optical characteristics in sea water column with the help of airborne lidars are presented. The approach used is based on the developed theory of retroreflected light pulse formation in scattering medium with angular anisotropy of volume scattering function and Saketts discriminability criterion; the effects of solar illumination, sea surface waves, and atmospheric backscattering are taken into account, as well as the internal noise factors of lidar transmitter and receiver. The recommendations are formulated for system parameters optimization for separate subsurface water layers detecting in various hydro-optical situations and different environmental conditions.

Russian airborne lidar for oceanography

The paper is devoted to consideration of the main airborne and ship LIDAR systems developed in Russia in the last years for sea water analysis and bathymetry of near coastal regions. The comparative analysis of the systems and their analogies from other countries are given. The level achieved in elaboration of separate elements of LIDARS is also examined (lasers, receiving optical systems, spectral selectors, cooling devices, and so forth).

Optimization of laser wavelength in oceanographic lidars

The recent developments in manufacturing of various types of lasers, including new modifications of Nd:YAG, Cu+ vapor, and dye lasers, are considered from the point of view of application in airborne systems designed for remote sensing of natural water bodies. The general expressions are given to analyze the effect of laser source wavelength on expressions and general optical detection theory based on Saketts D-index of discriminability, a criterion is formulated for optical choice of sounding radiation wavelength for airborne lidar systems which takes into account the sun light composition as well as spectral dependencies of PMT photocathod sensitivity, hydro-optical characteristics of sea water and bottom reflectivity. Several results are presented to compare the effectiveness of different laser sources for lidar bathymetry applications for various types of ocean waters and meteorological conditions.

Interpretation of some anomalies in the shape of lidar signals from upper sea-water layers

In a series of laser sounding experiments the registered shapes of retroreflected light pulses demonstrate an anomalously high levels of signals from isolated seawater layers. We propose here an interpretation for such peculiarities of echo-signal shape with the use of developed theory of backscattered light pulse kinetics in turbid medium. Our approach is based on the accounting of the angular anisotropy of the scattering in the back hemisphere and the geometrical conditions of typical lidar experiment, which determine the small angle divergence of collected light beam from the retro-reflection direction. According to the analysis presented below, the enhanced backscattering from isolated depth levels may be caused by high concentration of large biological particles (alga cells - coccolitophorids, diatoms, etc.) in the corresponding water layers. The explanation is shown to be consistent with the known unique measurements of volume scattering phase function in the vicinity of backward direction.

Remote sensing of subsurface layers of turbid seawater with the help of an optical lidar system

Vertical profiles of optical parameters in stratified sea water are known to demonstrate the presence of thin (units of meters) layers characterized by enhanced backscattering. Such layers may be formed by high concentration of large (tens of microns in diameter) suspended particles, alga cells (diatoms,m etc.) in particular. The intensity of light backscattered from within the layers makes it possible to identify them by the shape of lidar signals. On the base of developed theory of lidar echo-signal formation the analysis is presented of the scattering layers discriminability (Sakitts D-index) and recommendations for lidar parameters optimization are formulated. The optimal characteristics of lidar system for subsurface layers detection are shown to differ significantly from such characteristics for traditional bathymetrical airborne lidars.

Fluorescent products in high-density lipoproteins (HDL) and their association with other lipid peroxide products (LPPs)

The lipid peroxidation products of the lipofuscin type can be measured in plasma with the help of fluorimeters. Such products are increasing during whole plasm oxidation in parallel with other indices of lipid peroxidation damage. Preformed fluorescent products are located in all lipoprotein classes. The study of lipofuscin-type pigments fluorescence in HDL showed, that they contain substantial amounts of fluorescent compounds and that it rises in parallel with concentration of other lipid peroxidation products, especially thiobarbituric acid-reacting substances. Neither total plasma cholesterol, nor triglycerides influenced content of fluorescent products in HDL. The HDL subfractions contained different types of the fluorescent products but the bulk of these lipoproteins were almost free of them. The obtained data show that measurement of lipofuscin-type fluorescence in HDL gives a good and sensitive index of these lipoproteins damage by peroxidation.

Backscatter anisotropy and the shape of retroreflected lidar pulse from sea water

In several LIDAR sounding experiments, certain anomalies in the registered pulse shape were observed, such as the time delay between maxima of pulse of sea-water response and surface- reflected pulse, and unexpectedly high level of signals from isolated sea-water layers. These peculiarities cannot be explained with the traditional theoretical treatment of the echo-signals. In this paper, a new explanation of the return signals shape anomalies is presented. Our approach is based on the accounting of the angular anisotropy of the scattering in the back hemisphere and the geometrical conditions of the typical LIDAR experiments. We present computational data and laboratory measurement results related to enhanced backscattering by large coated particles suggested to model the optical properties of some algal cell species (diatoms, and so forth). The model calculations of the LIDAR signal shape show that such particles may be responsible for an anomalously high level of LIDAR signals from isolated sea-water layers.

Angular anisotropy and kinetics of light backscattering from discrete random media

The results of experimental study and theoretical treatment of the evolution of the backscattered light pulse in statistically homogeneous disordered medium are presented. Scattering kinetics was measured for water solutions of the latex microparticles with time-correlated photon-counting setup and ML Ar -laser. It is shown that backscattered pulse arrived to photo detector with essential delay with respect to the pulse reflected from the surface of the scattering medium. This delay is due to angular anisotropy of the scattering. Backscattering of non-coherent diffuse component of radiation propagating in forward direction develops in inner layers of the medium and determines the value and concentration dependence of the backscattered pulse delay. 1.