The article considers options for using electro-optical modulators as a device for shifting the frequency of the probing signal. Unlike acousto-optic modulators, which do not allow changing the modulation frequency, electro-optic modulators can change it over a very wide range, according to the form specified by the RF generator. At the same time, electro-optical modulators have disadvantages that require a special operating point controller that maintains the state of the modulator in a given position, regardless of environmental conditions.
A system of imaging of backscattered lidar pulses based on a SPAD camera developed at the IAO SB RAS is described. The main technical characteristics of the system are presented. Examples of 3 images of a single laser pulse with wavelength of 532 nm recorded by the SPAD camera with imaging array of 64 × 32 pixels from distances of 75, 90, and 285 m are given.
The report reviews the existing lidar methods and systems for measuring the wind speed vector. Examples of the successful application of Doppler systems are given and the choice of fiber technologies for constructing laser meters for wind speed and direction.
In this paper we consider the transformation of the trajectory of cloud formations in the system of the topocentric observer with their linear character of motion at a fixed altitude around the planet's surface.
The article describes instruments for measuring the height of the cloud base, which are widely used in meteorology, especially as meteorological support for aerodromes. It is noted that there is no single method by which the height of the lower cloud boundary is determined. The methods of processing signals for determining the height of the lower cloud boundary (applicable for automatic recording mode) are presented.
The paper deals with the problem of maintaining job opportunities optoelectronic devices in applications that require heating protective glasses. The author gives a comparison of different methods of heating for their efficiency and complexity in the design and manufacture of space heaters, as well as analyzes the characteristics of the products in the manufacture of both heaters and protective glasses themselves. This review will be of interest to designers and developers in the field of modern optoelectronic devices and systems with a wide range of temperatures during operation.
The paper deals with the problem of obtaining weak signals in terms of background noise and the possibility of reducing the influence of outside lighting probed volume nephelometer. The author offers a variety of ways: the use of the design features of a nephelometer, the restriction of the field of view of the system, the installation of hoods, the installation in the construction of light absorbers, the use of modulation of illumination, circuit solutions in the receiving part (active and passive filters), hardware and software solutions for the subtraction of the background portion of the signal from the received signal based on the previous state of the optoelectronic tract.
The article represents the description the problem of calibration meter height of cloud base in registration mode, multiple layers of clouds. The article provides an analysis of points of views of researchers on the possibility of creating a compact device to simulate several layers of clouds in the calibration meter height of the cloud base. The authors propose an original way to use fiber optic technology to simulate several layers of clouds. The paper describes the key benefits and features of this solution, as well as restrictions on the possibilities of its use.
In this paper we are talking about the possibility of increasing the accuracy of measurements of turbidity meter. The article analyzes the requirements of the light source being probed volume, as well as in calibration mode. Use as a pulsed light source of high power LEDs, collimator requires optimization which is devoted to this work. The main factor limiting the possibilities for creating the desired collimator are the dimensions of both the collimator, the one and only device. Considerable attention is paid to the uniformity of light-probed volume nephelometer.
The article seeks to examine the possibility of calibration of the compact meter of meteorological visibility range, methods other than the method of direct comparison. During the analysis, authors for the first time in the literature show that it is possible to use formazine for this, as a means for calibrating the meter of meteorological visibility IMDV).
The article is devoted to the optimization of the parameters of the meter of the height of the cloud base. The authors reveal the problem and possible ways to improve meter of the height of the cloud base. Particular attention is paid to improving the functioning of the device without changing the material base. Based on the analysis is determined by the wishes of the consumers' needs for additional product options.
In this article were consider problems of calibration and verification of a portable meter of height of the cloud base. We analyzed the characteristics of the operating conditions of calibration kits. Was reveal and provided the possibility of developing methods for the use of a compact calibration device. Based on the study, the authors proposed a technical way of implementation, formulated the basic characteristics, the sources and extent of error.
Developed and tested a simplified version of the definition of the cloud base height of the backscatter signal obtained in the laser meter height of the cloud base with eye-safe level of radiation intensity.
Plants constantly interact with environment, mainly, by means of photosynthesis and soil nutrition. The state of plant photosynthetic apparatus that reflects the general physiological state of a plant, can be analyzed remotely on a basis of laser-induced fluorescence using a fluorescence lidar. In this respect, a fluorescence lidar can be a technical means of remote sensing of the effects on vegetation including chemical soil pollution. Among a series of applications, of interest is development of a lidar technique for detecting the effects of oil products and mechanical disturbances. This paper is devoted to the application of the fluorescence lidar technique to monitoring mechanical and chemical impacts on the woody vegetation typical of Siberia. A physical basis of this technique is the red fluorescence of chlorophyll of green plants excited by the second harmonic (532 nm) of Nd:YAG laser. Red fluorescence of plants consists of two bands centered at 685 and 740 nm which is conditioned by functioning of two photosystems. As in situ experiments show, the indicated photosystems and, respectively, the fluorescence on these bands respond differently to feeding disturbances and mechanical impacts, making the increase in the fluorescence intensity informative. Time criteria of fluorescence characteristics were obtained at single and multiple effects on the vegetation. The paper describes a lidar system that meets the requirements for detecting the effects on vegetation.
The possibilities of applying a fluorescent lidar based on the second harmonic of a Nd:YAG laser to study vegetation under natural conditions are analyzed. The dynamics of development has been studied for several species of arboreous plants grown in West Siberia in a five-year measurement cycle. The fluorescent lidar developed has been used for identification of plant species and for investigation of fading caused by an adverse environment. It is shown that the fluorescent signal can be used for remote detection of plant stresses at earlier stages, when there are no visible symptoms. For the first time, the quantitative relations are established between the intensity of red nanosecond fluorescence and the chlorophyll concentration in needles and leaves of the most typical representatives of West Siberian arboreous plants. Fluorescent data were checked using the traditional spectrophotometric method. The spectrophotometric data and lidar measurements were used to calibrate the lidar, and this calibration has allowed the chlorophyll concentration in arboreous plants to be determined from the ratio of signals of laser-induced fluorescence.
The paper describes the fluorescent lidar created for monitoring of the atmosphere and for estimating the content of fluorescent components of organic aerosol. The lidar operation is based on the use of ultraviolet radiation of harmonics of Nd:YAG solid state laser for exciting the atmospheric fluorescence and the spectral analysis of the atmospheric fluorescence is used in the near ultraviolet and blue spectral range with the resolution of 2 nm. The lidar was found to be efficient for remote analysis of organic aerosol occurring as a result of vegetation emission of secondary metabolites to the atmosphere. Fluorescence spectra processing allows us to select some organic compounds, which molecules contain 7 and more carbon atoms.
Taking into account the availability of interconnection between organic aerosol and vegetation, in lidar the second harmonic of Nd:YAG laser is also used for exciting the fluorescence of vegetation covers. In this case the receiving system detects the fluorescence of vegetation in the red spectral range conditioned by the chlorophyll of vegetation. Simultaneous detection of the fluorescence from the atmosphere and from vegetation makes it possible to obtain data on the interaction of the atmosphere and underlying surface covered by vegetation. It has been found that a disruption in the vegetation feeding or the impact of pollutions on vegetation resulted in a sharp increase of the fluorescence intensity of vegetation chlorophyll in the red spectral range and in the simultaneous appearance of organic aerosol in the atmosphere adjacent to vegetation in the region of negative impact.
A technique is developed to plan and conduct lidar profiling of temperature and humidity by the DIAL (differential absorption lidar) method in the lower troposphere. The technique proposed has been tested in the near JR region when designing a meteorological lidar based on the Ti:Sapphire laser. The DIAL and correlation methods were used in the meteolidar complex for measurements of the main atmospheric parameters: temperature humidity wind velocity and direction. The possibility of this lidar complex for remote determination of the main meteorological parameters is investigated. The accuracy ofthe measurements is estimated.
The comparative research of the chlorophyll contents for a number of arboreous plants has been carried out using traditional spectrophotometric and fluorescent laser techniques. Seasonal changes are analyzed in the net chlorophyll content during the sprint-summer period for coniferous and deciduous wood plants. The changes in the chlorophyll contents due to needles and leaves fading are observed. The experimental results are obtained using the spectrophotometric and lidar techniques to study the seasonal dynamics of chlorophyll and pigment complex destruction in the course of needles and leaves fading. Analysis has shown that the results obtained different methods are identical.
The objective of Russian space project Tectonica-A is creation of automated lidar for studying aerosol anomalies, mainly, in the low atmosphere. By such anomaly is meant heterogeneity both of the aerosol concentration and its microphysical properties. Therefore, this project assumes that a small spacecraft will be equipped with multifrequency (wavelength range from 0.35 to 1.06 micrometers ) lidar. The lidar is aimed to investigate the aerosol fields formed during tectonic (including seismic) processes and catastrophes. Using the lidar high potentiality providing detection of local emissions in the low atmosphere. The project execution is in the stage A-B (draft design). The lidar installation is oriented to the platform MKA-200. Simultaneously with the lidar creation, the methods are developed on the basis of its mini-prototype. In October, 1999, the spatial, temporal boundaries of aerosol anomalies near Rostov-on-Don break (West Caucasus) were investigated during artificial and natural earthquakes. Simultaneously, gases show (radon, first of all) and fluctuations of atmospheric electric fields were estimated. Some correlation between aerosol, gas, and electric anomalies has been found, which underlines once again a priority of aerosol from the standpoint of remote optical monitoring of tectonic processes. Based on the obtained results, the methodological aspects of space laser sensing of aerosol anomalies are discussed in the report. The requirements to the lidar Tectonica-A and space experiments conducting are refined as well.
The comparative research of the chlorophyll contents for number of wood plants by traditional spectrophotometric and fluorescent laser methods is carried out. The seasonal changes of the chlorophyll sums in the spring-summer period at coniferous and deciduous wood plants are analyzed. The supervision over changes in the chlorophyll contents in connection with a withering of needles and leafs are carried out. The experimental results are received by spectrophotometric and lidar methods of study of a course of chlorophyll seasonal dynamics and pigment complex destruction of during a withering of needles and leafs of wood plants. The results of the joint analysis have shown identity of results received essentially by various methods.
The comparative research of the chlorophyll contents for number of wood plants by traditional spectrophotometric and fluorescent laser methods is carried out.The seasonal changes of the chlorophyll sums in the sprint-summer period at coniferous and deciduous wood plants are analyzed. The supervision over changes in the chlorophyll contents in connection with a withering of needles and leafs are carried out. The experimental results are received by spectrophotometric and lidar methods of study of a course of chlorophyll seasonal dynamics and pigment complex destruction of during a withering of needles and leafs of wood plants. The results of the joint analysis have shown identity of results received essentially by various methods.
The carried out experimental measurements of structures of speed and the directions of a wind with the help created meteorological lidar MEL-01 have confirmed perspective of its use for sounding of bottom troposphere. The results of numerical modeling of sounding of the atmospheric temperature and humidity profiles by differential absorption method in the near IR spectral range by means of the MEL-01 meteorological lidar show that the three-frequency method using the absorption lines from the band 0.72 in tropics and mid-latitude summer can compete with the two-frequency method of separate sounding of temperature and humidity. Only the two-frequency method is practical in the Arctic winter conditions. The absorption band of 0.94 is only weakly suitable for sounding in the atmospheric boundary layer.
The aim of the project `Tectonica-A' is the development of the technique and the creation of a spaceborne lidar for determining the sites of enhanced concentration of surface aerosols. The lidar data combined with the data of different sensors (spaceborne and ground-based) will be used for the short-term forecast of the earthquakes. Using the requirements for the lidar `Tectonica-A' the computer simulation was made of the operation of the elastic scattering multifrequency lidar in orbit at 600 km altitude. The need for selection of no less than three sounding wavelengths in the range of 300 - 1000 nm is shown. The lidar potential is justified to meet the demand for the necessary space resolution. Besides, the program of physical modeling of the lidar `Tectonica' was developed for the study of dynamics of the aerosol concentration in the atmospheric boundary layer in the seismic active area of Russia (the lake Baikal). The optical observations are combined with the simultaneous measurements of the electromagnetic radiation intensity of the Earth's crust.
Experimental investigations of the fluorescence intensity of plants in red spectral range induced by the laser radiation have been carried out. Dependence of the quantum yield of chlorophyll a fluorescence on plant species has been established and investigated. The largest range of seasonal variations of the fluorescence intensity was observed for the deciduous trees. Seasonal variations of the fluorescence intensity have the tendency to insignificant variations for the coniferous trees. Application of the fluorescence method to the remote specific categorization of the plant tissue and determination of the chlorophyll content is shown to be promising.
Experimental investigations of the fluorescence intensity of plants in red and ultraviolet spectral ranges induced by the laser radiation have been carried out during one year. Dependence of the quantum yield of chlorophyll a fluorescence on plant species has been established and investigated. The largest range of seasonal variations of the fluorescence intensity was observed for the deciduous trees. Seasonal variations of the florescence intensity have the tendency to insignificant variations for the coniferous trees. Application of the fluorescence method to the remote specific categorization of the plant tissue and determination of the chlorophyll content is shown to be promising.
Results of the statistical analysis of height distribution of the atmospheric aerosol in the boundary layer are presented. Data on the lidar sounding obtained in Tomsk (56 degree(s)N, 85 degree(s)E) were used as starting data. Vertical stratification of atmospheric aerosol is found following the modified method of clustering of arguments.
The results of floodlight sounding of atmospheric layers with spatio-oriented nonspherical particles are presented in this paper. It is shown that components obeying the regularities of diffuse scattering and specular reflection occur in the scattered radiation as a result of interaction of the directional optical radiation with such a layer. Depending on observational conditions, the intensity of specularly reflected component might be several times higher than the intensity of radiation diffusely scattered in the same direction.
Experimental investigations of the fluorescence intensity of plants in red and ultraviolet spectral ranges induced by the laser radiation have been carried out during one year. Dependence of the quantum yield of chlorophyll a fluorescence on plant species has been established and investigated. The largest range of seasonal variations of the fluorescence intensity was observed for the deciduous trees. Seasonal variations of the fluorescence intensity have the tendency to insignificant variations for the coniferous trees. Application of the fluorescence method to the remote specific categorization of the plant tissue and determination of the chlorophyll content is shown to be promising.
Surface forest fires (SFF) is the most common natural type of the forest fire causing a great ecological and economic damage. Although quite a lot of experimental works have been devoted to an investigation of SFF, a problem of a dominating mechanism of transferring energy from the zone of reaction to a forest fuel has not been solved yet. Exact profiles of the combustion product concentrations in the fire front are not known, and limiting conditions of its spread have not been properly investigated. To detect forest fires passive optico- electronic systems located on space apparatus are coming into use. However, to estimate the efficiency of space techniques, identification methods, classification and prediction of the forest fire development it is necessary to know thermal flows in the assigned spectral intervals, attenuation of an irradiation by an atmosphere, by particles of smoke and crowns of the trees, efficient combustion areas depending on the type of the fire and some other characteristics. Besides, it is necessary to take into account that a combustion process of the forest fuels depends on their density, moisture content, initial temperature and humidity of the air as well, speed and direction of the wind, the angle of terrain relief slope. Investigation of SFF in the natural, large scale experiments is complicated because of the bad reproduction of the results and considerable dependence of the combustion parameters on external factors. In general this problem is solved by means of laboratory devices which allow to model partly the conditions of the surface forest fire initiation and spread. For example, in the works set-ups for physical modeling SFF in specialized aerodynamic pipes are described. However, this method has unavoidable drawback caused by the fact that a real process of the forest fuel combustion in an open space is modeled by a combustion of the forest fuel in a half-closed space where the experiments are made. Closeness of the space in specialized aerodynamic pipes results in a change of temperature and composition of the medium and influences velocity fields of the fire front as a result of the traction force change in the area of SFF. Hoover, experimental works on investigation of the fires in laboratory conditions continue, new laboratory set-ups being made allowing to exceed the range of investigating forest fuel combustion with more exact approximation to the real conditions. In contrast to the natural investigations laboratory experiments can be carried out all the year round with less material expenses.3122
Experimental research of red fluorescence of tree's tops, inducted by laser radiation 0.53 micrometers in summer - autumn period are carried out. Specific dependence of the fluorescence quantum output of chlorophyll a is found out and investigated. The seasonal course of fluorescence intensity tends to complete attenuation for deciduous trees and insignificant changes for coniferous trees. It is shown perspective of application of a fluorescence method for remote species selection of vegetable tissues and definition of the chlorophyll content.
The results of floodlight sounding of atmospheric layers with spatio-oriented nonspherical particles are represented in this paper. It is shown that components obeying the regularities of diffuse scattering
and specular reflection occur in the scattered radiation as a result of interaction of the directional optical radiation with such a layer. Depending on observational conditions the intensity of specularly reflected component may be several times higher than the intensity of radiation diffusely scattered in the same direction.
At a lidar sounding of atmosphere meteorological parameters, (wind velocity and direction profile) the precipitation more often is considered as a hindrance, which limits the distance and accuracy of the measurements and in some instances performs the impossible measurements. But in the course of investigations it has been found that in certain situations, the precipitation increase efficiency of lidar sounding. In this case the distance and accuracy of sounding are increased. Primarily this is true for precipitation, which has the intensity no more than 1.5 mm/h. Furthermore, the possibility of determinations of the microstucture and integral characteristics of precipitation area is existed. The investigations were performed using the correlation scanning three-path lidar with vertical scheme of sounding. In the course of measurements the spatial-temporal series reflected by precipitation optical signals were amassed. The handling of the lidar data was based on the correlation-spectral method. The study of the optical signals reflected from preciptiation showed that the increase of the wind velocity sounding efficiency is available by amplification of the signal fluctuation components. Limitations on the rain rate are caused by powerful rain. A maximum of the dropsize distribution function is displaced inside of the high quantities which are not carried by air flows and useful information for the estimation of wind velocity gives the raindrops with dimensions no more than 0.6 mm in diameter. As the lidar allows to make a vertical cut of the precipitation area, that it was seen the moving of forward and reverse fronts of the precipitation area at the spatial range of the optical signals. From a comparison of the front positions in different times the drop speed of the different rain group is determined. This allowed us to estimate the range size raindrops and raindrop size distribution function was determined. The knowledge of precipitation microstructure parameters allows obtained integral characteristics of precipitation area: rain rate (mm/h), watery (g/m3), raindrop concentration (1/m3).
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