Laser Sounding Research Articles

Advantages of an Additional Raman Channel in Laser Sounding at Wavelengths of 355–1064 nm for Retrieving Microphysical Parameters of Atmospheric Aerosol

Advantages of an Additional Raman Channel in Laser Sounding at Wavelengths of 355–1064 nm for Retrieving Microphysical Parameters of Atmospheric Aerosol

Variability of the Cloud Base Height over the Territory of Western Siberia Based on Laser Sounding Data for the Period 2010–2021

Variability of the Cloud Base Height over the Territory of Western Siberia Based on Laser Sounding Data for the Period 2010–2021

OPTIMIZATION OF ONBOARD LASER-FLUORESCENT CONTROL OF ENVIRONMENT POLLUTION BY OIL AND OIL PRODUCTS

The article is devoted to the optimization of sea surface pollution control using the laser-fluorescence method. Two optimization variational problems for remote detection and assessment of sea surface pollution by oil and oil products have been compiled and solved using the fluorescence method. The solution of the first problem on the optimal choice of the wavelength of the emission signal was carried out according to the criterion of achieving maximum information content. The solution of this problem made it possible to determine the wavelength in multipoint laser sounding of sea waters. The solution of the second optimization problem made it possible to determine the optimal form of the dependence of the optical thickness of atmospheric aerosol in the used wavelength range of optical fluorescent emission.

Investigation of the protective capabilities of glass from laser sounding depending on its elemental composition

One of the most vulnerable issues in the technical protection of information is to obtain data via leakage through the opto-electronic channel.
 In this paper, studies of the protective capabilities of glass from laser sounding depending on its elemental composition were carried out using such indicators as the coefficients of reflection and absorption of the laser beam by the window glass.
 As a result of the work, an experimental installation based on a continuous solid-state laser was assembled.
 The study of the elemental composition of window glass, which is produced by modern industry, X-ray fluorescence method and the study of the coefficients of reflection and absorption of glass samples in the experimental setup showed that the studied window glass chemically belongs to quartz (silicate).
 All chemical elements involved in its formation can be divided into 3 groups: glass-forming, transitional, modifiers, which affects the optical properties of the studied glasses, as the elements used have different not only qualitative but also quantitative parameters.
 Absorption increases if the number of chemical elements that exhibit amphoteric and non-metallic properties and have (-charge) decreases, and increases if the number of chemical elements in the glass that exhibit the most alkaline, alkaline earth properties and in which the radius of cations (+ions) increases.
 Systematization of the elemental and quantitative composition of the studied window glass in accordance with the periods and groups of the periodic table of chemical elements, enabled the relationship between the electronic structure of chemical elements and the protective properties of glass

Model of an electro-optical devices in the conditions of its active pulsed laser sounding as an object with a non-local reflection

Model of an electro-optical devices in the conditions of its active pulsed laser sounding as an object with a non-local reflection

Studying How Plasma Jets are Generated in a Plasma Focus

Plasma bunches with the characteristic size of approximately 1 mm and electron density larger than 1019 cm–3 are registered by the laser sounding methods on a Mather-type plasma focus (PF). The bunches appear after the collapse of the plasma column and move along the discharge axis from the anode with the initial velocity of 2 × 107 cm/s. The generation of these bunches is mainly caused by the axial displacement of the plasma during development of the Rayleigh–Taylor instability on the pinch. The plasma jets in the second half-period of discharge are also registered. Moreover, the layered plasma structures are revealed at the decrease in the discharge current.

Estimation of the Absorption Effect on Light Scattering by Atmospheric Ice Crystals for Wavelengths Typical for Problems of Laser Sounding of the Atmosphere

Results of analyzing the numerical calculation of light scattering matrices for ice crystals of arbitrary shape with allowance for absorption are presented. The matrices are obtained within the framework of the geometrical optics approximation. The effect of absorption on properties of light backscattering is estimated for problems of laser sounding of the atmosphere. The results demonstrate that taking into account the absorption when the wavelength is shifted inward the IR range leads to a decrease in the scattered radiation intensity. The effect of absorption for wavelengths of 0.355 and 0.532 μm does not exceed hundredths of a percent; for 1.064 μm, several percent; and for the near IR range, it can exceed tens of percent.

Effectiveness of Combined Laser and Gas Chromatographic Remote Detection of Traces of Explosives

The results of remote detection of objects containing explosives with a lidar detector of traces of explosives in combination with a portable express gas chromatograph are presented. It is shown that the lidar detector of traces of explosives confidently detects the simulators of TNT, hexogen, and PETN from a distance of 5 m when sounding the surface of a sample. Laser action on the sample surface causes desorption of vapors, which are reliably detected by the gas chromatograph. It is shown that the joint use of the laser sounding and gas chromatography techniques makes it possible to increase the reliability of detection of explosives. The prospects of using the gas chromatography in the development of laser sounding techniques are determined.

Siberian lidar station: instruments and results

The Siberian Lidar Station created at V.E. Zuev Institute of Atmospheric Optics and operating in Tomsk (56.5° N, 85.0° E) is a unique atmospheric observatory. It combines up-to-date instruments for remote laser and passive sounding for the study of aerosol and cloud fields, air temperature and humidity, and ozone and gaseous components of the ozone cycles. In addition to controlling a wide range of atmospheric parameters, the observatory allows simultaneous monitoring of the atmosphere throughout the valuable altitude range 0–75 km. In this paper, the instruments and results received at the Station are described.

Контроль загрязнений сточных вод с использованием двухчастотного лазерного зондирования

Optical methods for analysis of non-uniform liquid mediums have been considered, correlational and functional connections between the optical density and parameters characterizing industrial wastewaters’ type, content and pollution level have been investigated. Have been demonstrated main tendencies related to development of technology and equipment for optoelectronic control of industrial wastewaters’ pollution. Approximation of emission and absorption spectra for optical radiation’s emitter and receiver using the known Laplace function allows carry out calculations for a choice of optical couples’ coordinated parameters for two-frequency optical control, and as a result to increase reliability of identification for a type and degree of pollution for wastewaters and industrial effluents in comparison with use of one emission source. The method of pollution two-frequency laser sounding differs in improved control characteristics compared with the ones offered in patents, as well as in scientific and technical literature.

Adsorption laser meter of water transport velocity in capillary systems of a plant

The article provides the results of measurements of the velocity of the upward water flow in capillary xylem bundles by laser sounding for cucumber plants (hybrid TSHA-575). An adsorption laser meter of water flow velocity in plants was developed. We showed experimental and calculated dependences of linear velocity of xylem flow on the level of gradients of bioelectric potentials along the stem of a plant. Comparative analysis of the obtained experimental results with the model was carried out.

Multifrequency lidar sounding of air pollution by particulate matter with separation into respirable fractions

A technique is considered for retrieving the spatial distributions of respirable fractions of aerosol in the lower atmosphere on the basis of multifrequency lidar sounding data without the use of additional aerosol optical and microphysical parameters along a sounding path. For this purpose, it is suggested to replace the spectral values of the aerosol extinction coefficient involved in lidar equations with the linearly independent parameters of their approximation, and retrieve the spatial distributions of these parameters from the numerical solution of the set of equations composed of all wavelength-time lidar signal samples. As a result, the number of unknowns in the set of equations to be solved is significantly reduced, and its matrix becomes overdetermined, which can be used for selection of physically reasonable values of the aerosol backscattering phase function at the lidar operating wavelengths. An assumption that there are two segments at the sounding path with similar aerosol extinction coefficient profiles is used to determine the lidar calibration constants. An algorithm is suggested for the search for these segments by the wavelength-time structure of a lidar signal. The inverse problem of aerosol light scattering is solved on the basis of stable regression relations between the concentrations of respirable aerosol fractions and approximation parameters of the aerosol extinction spectrum. The stability of the technique developed to the calibration errors and spatial variations in the aerosol backscattering phase function is shown in numerical experiments on laser sounding of aerosol.

Observations in Lidar Station of St. Petersburg State University for Ecological Safety Studyies

The solution of many problems associated with the air pollution, radiative regime of the earth's surface and atmosphere, global and local environmental changes and climate, facing humanity in the early 21st century, require detailed and regular information on atmospheric aerosol and gaseous pollutants in the atmosphere. For monitoring atmospheric pollutants especially effective were the methods of laser sounding of the atmosphere, which provide a vertical profile of aerosol parameters to a height of 20 km In this regard, at the beginning of the 21st century created a continental networks of lidar sounding stations. Over Europe there is a network EARLINET. Laser station, built on the basis of St. Petersburg State University has become the first Russian station that acceded to the European research network. The article briefly presents the technical features of the equipment and demonstrates the first results of the observations.

Technique for determining mass concentrations of aerosol fractions in the surface air from multifrequency lidar sounding data

A technique for determining mass concentrations of aerosol particles smaller than 1.0, 2.5, 10, and 30 µm in the surface air is suggested. The technique involves remote lidar sounding of the atmosphere at the wavelengths λ = 0.355, 0.532, 1.064, 2.13 µm, retrieval of the spectral and spatial distributions of the aerosol extinction coefficient from the lidar signals, and their conversion to the spatial distributions of the concentrations of aerosol fractions on the basis of regression relations between optical and microphysical aerosol parameters. To improve the accuracy and stability of the solution of a system of lidar equations, the calibration constants and lidar ratios at the wavelengths of the sounding radiation are chosen taking into account the multicollinearity of the spectral aerosol extinction coefficients, which is expressed in the form of a multiple regression equation. The regressions were derived within the World Meteorological Organization’s optical model of urban aerosol under wide variations in model parameters which characterize the particle size distribution and the complex refractive index of the aerosol matter. Numerical experiments on remote laser sounding of the mass concentration of aerosol fractions in the atmosphere have shown the robustness of the technique proposed.

Лазерная система предупреждения аэрозольных выбросов

Presented system simultaneously controls concentration and size distribution function of particles by means of twowave
 laser sounding on the basis of spectral clarity method for increase of probability of aerosol emissions detection and
 identification at early stages of formation. Due to the system’s operational algorithm its response time does not exceed 300
 sec. Laser system of prevention of emissions above the allowable level over industrial facility allows to resolve two main
 issues: prevention of environmental pollution and elimination of raw materials losses in the form of dust emissions carried
 away into the atmosphere.

Application of an overtone CO laser for remote gas analysis of the atmosphere

The possibilities of using an overtone CO laser for remote laser sounding of gaseous atmospheric components by the differential absorption method are studied. The informative wavelengths for trace gas sounding are found. The spatially and spectrally resolved lidar signals are calculated in the range of the selected wavelength for vertical sounding paths. Test experiments on application of the differential absorption method for atmospheric gas sounding with the use of an overtone CO laser are carried out.

A mechanical light chopper based on a hard disk drive for systems of laser sounding of the atmosphere

An easily manufactured high-speed mechanical chopper based on a Maxtor D740X-6L hard disk drive with a rotation speed of 7200 rpm is described. It is shown experimentally and theoretically that the switching time of a light beam with a diameter of 0.8 mm is ∼20 μs. The described chopper can be used in systems of laser sounding of the atmosphere for protection of photodetectors against a high-power backscattered signal from a near zone of the sounding line, as well as in other problems where fast mechanical switching of a light beam is required.

Femtosecond laser radiation frequency converters for lidar monitoring of the atmosphere

The possibility of using biaxial nonlinear crystals in the optical converters of femtosecond radiation pulses for laser sounding of the atmosphere has been studied. A method of broadband monitoring of the atmosphere composition using the differential optical absorption spectroscopy technique is described. The results of the numerical simulation of the lidar monitoring of gaseous components of the atmosphere using frequency-converted femtosecond laser radiation pulses are presented.

Technique and results of measuring surface-acoustic-wave reflection coefficients with the use of laser sounding

A technique of measuring the surface-acoustic-wave (SAW) reflection with the use of a laser sounding facility containing a reference diffraction grating is described. The characteristics of the SAW reflections from the edges of YX-cut quartz-crystal substrates with the end faces beveled at various angles are measured. In addition, the frequency dependence of the magnitude of the SAW reflection coefficient for reflection from periodic gratings in the form of lithium niobate metal strips are measured.

LOSA-MS lidar for investigation of aerosol fields in the troposphere

The LOSA-MS combined small-sized single-wavelength backscatter lidar is described whose operation is based on the effects of Raman and elastic scattering. To extend the range of sounding, lidar returns are registered simultaneously in analog and photon counting regimes. A photodetector system for wavelength and polarization selection of lidar signals is described. The basic physical principles of laser sounding and methods of solving the lidar equation to retrieve information on the optical-physical state of examined objects are presented. Examples of using the LOSA-MS lidar for monitoring of spatiotemporal distribution of aerosol pollutants above an industrial center are given together with examples of investigation of the aerosol field structure under background atmospheric conditions.