The German lake district 'Mecklenburger Kleinsceenplatte' between Berlin and Rostock shows a great variety of lakes having different tropical states. Remote sensing of water quality is investigated to help monitoring the lake waters and to guide the water sampling more carefully over space and time. Satellite data of the Indian Remote Sensing Satellite of summer 1996 are analyzed for a general overview of the variety of lake water within the test area. To get more quantitative information hyperspectral scanner data of the Compact Airborne Spectrographic Imager are investigated. For these data a ratio of two bands pointing to chlorophyll absorption at 680 nm and a hull function over the absorption band have been applied. The results could be well related to the ground truth data taken by the Institute of Fresh Water Ecology in Brandenburg. They show differences in chlorophyll content even in December, a season of minimal bioproduction. Thus, further research in the summer season is promising to get good results in estimation of water quality parameters.

Hydrographic conditions are often characterized by large amounts of dissolved and particulate matter. These substances influence the optical properties of seawater, an the radiative transfer in the water column. Attenuation coefficient and fluorescence are optical parameters which depend sensitively on suspended and dissolved substances. These measurements are of interest in determining of absorbing, scattering and fluorescent matter. Two new probes have been developed for this approach: a multispectral attenuation meter and a multichannel fluorometer. Particular emphasis has been put on the long-term stability of the optical set-ups. Areas of application of these instruments are bio-optical and bio-chemical studies in estuaries and coastal zones as components of profiling probing systems or autonomous stations.

The initial phase of the chlorophyll fluorescence induction kinetics provides information about the action of herbicides. Measurements on algae and on wheat show a change in the curve shape in the first 60 ms when the herbicides DCMU, atrazine, and terbuthylazine are applied with concentrations between 0.5-200 (mu) g/l. As the measurements are non-destructive, repeated measurements at one site of the wheat leaf can monitor the increasing herbicide concentration after the application to the roots. An empirical parameter B_r derived from the fit of the initial phase with two exponential functions estimates the degree of the inhibition induced by the herbicide. The measured curves can also be analyzed in terms of the usual PS-model. This yields the parameter B_b which estimates the relative contribution of the blocked PS-centers to the fluorescence. As both parameters, B_b and B_r, exhibit an equivalent course in their dependence on the herbicide concentration, they scale the relative portion of the blocked PS-centers for a given herbicide concentration.

The ENEA group has participated to the second ICES/IOC workshop on in situ growth rates of dinoflagellates, held at the Kristineberg Marine Research Station. The laser induced fluorescence (LIF) emission of natural communities and cultures has been monitored in vivo to obtain information on the algae species, characterized by different pigments contents, and on their photosynthetic activity, which is related to the growth rate and biomass production. A laser fluorometer and a lidar system, used for local and remote LIF excitation of phytoplankton, have been operated during the marine campaign, both exciting the sea water in the UV. In particular, the lidar fluorosensor has been equipped with a laser transmitter specifically designed to operate differentially in the pump-and-probe mode, which allows to directly measure in vivo the chlorophyll fluorescence quantum yield. Experiments were conducted on two mesocosms containing the natural community with addition of nutrients. Chemical methods have been used for calibration of the two laser apparata. Results of the campaign are presented, together with the lidar data collected from the sea surface in crossing two nearby fjords along a selected sea transect.

By the end of 1993 the Federal Ministries of Transport and Defence put a second generation maritime surveillance system into service for long-term operation in the North Sea and the Baltic Sea. The system consists of a DO 228-212 aircraft and of a side-looking airborne radar, a microwave radiometer, a UV/IR line scanner, and a laser fluorosensor. The main purpose of the laser fluorosensor is the detection and classification of oil spills on the sea surface. In addition, dissolved organic matter and phytoplankton pigments can be investigated while the aircraft is performing long-range surveillance flights. The hydrographic data are analyzed by geostatistical algorithms, which exploit the spatial correlation of the data to estimate the 2D distribution and the prediction variance of the examined property. As an additional information about the reliability of the results, the prediction variance is accessible. In this way, a detailed illustration of hydrographic conditions in coastal waters can be achieved. In this article, we discuss problems that arise if the condition of statistical uniformity is not met by the data. A possible way to handle these data is demonstrated on a data set measured in the North Sea.

Lidar monitoring of surface waters has usually been applied to fluorescent and nonfluorescent soluble chemicals can be investigated. Two signals have to be measured, the total fluorescence lidar intensity L, which is characterized by long path-lengths of the laser radiation in the water column, and the fluorescence F, which originates from the first layers immediately below the water surface. The ratio of both intensities F/L yields the total attenuation coefficient at the laser wavelength considering also nonfluorescent substances besides fluorescent ones. A simple experiment in the laboratory was performed using a nitrogen laser. Water samples containing algae and a defined amount of humic acid were polluted with fluorescent quinine sulphate and nonfluorescent azobencene and p-nitrophenol down to ppb-concentrations. Synchronously, the attenuation coefficients were measured by conventional absorption spectroscopy. Good correlations between the conventional and the lidar-derived attenuation coefficients were achieved, described by squared correlation coefficients of r² > 0.95. The F/L ratio seems to be a good tool in lidar monitoring of dissolved chemicals in waters.

We have measured fluorescence from a waveguide formed by a falling cylindrical stream of liquid. The configuration is suited to taking measurements from liquids with any refractive index, such as aqueous solutions. The parameters which determine the stream stability have been investigated, and the optical collection efficiency has been mathematically modelled. We have produced streams up to 350 mm long with a 2.5 mm diameter, and measured a fluorescence collection enhancement factor of 9 from a 100 mm long, 1 mm diameter stream.

This paper reports on novel solutions to problem of in situ, real-time measurements in water without chemical enrichment steps. We have developed a photoacoustic and three miniaturized photothermal systems in our laboratory, allowing the construction of microstructured, miniaturized, adjustment-free and user-friendly analytical microprobes. The new systems are: photoacoustic spectroscopy, photothermal interferometry, thermal lensing and photothermal deflection spectroscopy. The determined analytes are pesticides, polycyclic aromatic hydrocarbons, textile dyes and iron in natural, ground and drinking water.

The development of surface-enhanced Raman scattering substrates suitable for in situ environmental analysis is presented. Sol-gel techniques are introduced to improve the mechanical stability of an existing active substrate type, to develop a new type of SERS active medium and finally to improve the sensitivity of substrates by providing a controllable coating. Two substrate types are discussed. The first consists of a glass slide covered with aluminium oxide particles which is then coated with gold.In the second type, a gold metal colloid is encapsulated within a porous thin film sol-gel structure. The sol-gel substrates were optically characterized and both substrates were tested in the laboratory. The mechanical stability of the new substrates is compared with that of conventionally prepared substrates and results are presented for pyridine, toluene and chlorobenzene in artificial sea-water.

In recent years, accidents of ships with chemical cargo have led to strong impacts on the marine ecosystem, and to risks for pollution control and clean-up teams. In order to enable a fast, safe, and efficient reaction, a new optical instrument has been designed for the inspection of objects on the seafloor by range-gated scattered light images as well as for the detection of substances by measuring the laser induced emission on the seafloor and within the water column. This new lidar is operated as a payload of a remotely operated vehicle (ROV). A Nd:YAG laser is employed as the light source of the lidar. In the video mode, the submarine lidar system uses the 2nd harmonic laser pulse to illuminate the seafloor. Elastically scattered and reflected light is collected with a gateable intensified CCD camera. The beam divergence of the laser is the same as the camera field-of-view. Synchronization of laser emission and camera gate time allows to suppress backscattered light from the water column and to record only the light backscattered by the object. This results in a contrast enhanced video image which increases the visibility range in turbid water up to four times. Substances seeping out from a container are often invisible in video images because of their low contrast. Therefore, a fluorescence lidar mode is integrated into the submarine lidar. the 3rd harmonic Nd:YAG laser pulse is applied, and the emission response of the water body between ROV and seafloor and of the seafloor itself is recorded at variable wavelengths with a maximum depth resolution is realized by a 2D scanner, which allows to select targets within the range-gated image for a measurement of fluorescence. The analysis of the time- and spectral-resolved signals permits the detection, the exact location, and a classification of fluorescent and/or absorbing substances.

Multiparametric optical assay (MOA) can provide further progress in studies and control of natural disperse systems (DS) such as water and air. MOA includes the nondestructive analysis of DS by different optical methods such as refractometry, absorption, fluorescence, light scattering. Taking into account an optical theory and modern technologies of data interpretation can help to elaborate methods for on-line optical control of complex DS. It is in accordance with fiber optics development. Bank of optical data for DS (BODDS) is an informative base of MOA. The goal of BODDS is computer processing of DS analysis, systematization, statistical study of data and solving of inverse physical problems by different ways. At the analysis of unknown polycomponent DS, for example, water with dangerous impurities of oil, bacteria or viruses, etc., the comparison of measured parameters with known one can help us to identify the unknown system.

The recent developments of airborne imaging spectrometers, currently mostly designated hyperspectral imagers, in the spectral regime from 400-2400 nm revealed and proved an enormous application potential for remote sensing of vegetation in particular. Current spaceborne instrument developments and soon mission will expand these applications to regional and global scale surveys and monitoring. Hyperspectral imagers covering the a.m. spectral range promise to represent the ideal future remote sensing tool for vegetation type and status monitoring. The paper starts with a compilation of relevant applications - with emphasis on vegetation and soils - and their particular spectral and radiometric requirements which has been established by the main author recently as part of a Dornier Satellitensysteme (DSS) in-house activity, including a survey of existing and planned instruments of this type. To the possible extent, airborne measurement data from existing instruments will be included to underline the application potential. The second part will provide an insight into current development activities at DSS, mainly as results of ESA contracts, covering instruments such as ROSIS, HRIS demo model and current PRISM studies. The two latter instruments are ideally suited for vegetation monitoring in terms of pixel size, spectral resolution and range from 450-2350 nm, and radiometric performance. An outlook will conclude the paper for future developments and planning for operational hyperspectral missions.

In the frame of the special yield estimation, a regular procedure conducted for the European Union to more accurately estimate agricultural yield, a project was conducted for the state minister for Rural Environment, Food and Forestry of Baden-Wuerttemberg (Germany) to test remote sensing data with advanced yield formation models for accuracy and timelines of yield estimation of corn. The methodology employed uses field-based plant parameter estimation from atmospherically corrected multitemporal/multispectral LANDSAT-TM data. An agrometeorological plant-production-model is used for yield prediction. Based solely on 4 LANDSAT-derived estimates and daily meteorological data the grain yield of corn stands was determined for 1995. The modeled yield was compared with results independently gathered within the special yield estimation for 23 test fields in the Upper Rhine Valley. The agrement between LANDSAT-based estimates and Special Yield Estimation shows a relative error of 2.3 percent. The comparison of the results for single fields shows, that six weeks before harvest the grain yield of single corn fields was estimated with a mean relative accuracy of 13 percent using satellite information. The presented methodology can be transferred to other crops and geographical regions. For future applications hyperspectral sensors show great potential to further enhance the results or yield prediction with remote sensing.

In this paper a summary of results obtained using ground- based and airborne microwave radiometers and airborne radars on agricultural crops is presented. The experiments took place on two agricultural areas, close to Florence. The capability of both sensor types to identify different crop categories and to detect the crop growth has been analyzed. A systematic investigation, aiming at identifying the correlation between multifrequency microwave backscatter and emission and vegetation biomass, was carried out. In particular, some relationships obtained between emission and plant water content of some crop types are presented and explained using a simple model based on radiative transfer theory.

The laser induced chlorophyll (Chl) fluorescence in vivo at the steady state was investigated as function of the light intensity impinging on the leaf. It was used a diode laser, with pulse duration in the 10 microsecond(s) -10ms range, emitting at 635 nm, and a nitrogen-pumped dye laser, with pulse duration of 5 ns, emitting between 440 and 635 nm. With both excitation sources, it was observed that the total Chl fluorescence increases with increasing the light intensity to a maximum reached at about 300 micrometers ol m^-2s^-1, then it decreases to values close to the dark fluorescence F₀. The Chl fluorescence spectrum was seen to vary in shape by changing the excitation wavelength from 440 to 635 nm because of change in the fluorescence reabsorption process at the 685 nm band. Light intensity at controlled temperature, the ratio between the shorter wavelength, at 685 nm, and the longer wavelength fluorescence bands, at 730 nm, as well as the total fluorescence intensity was seen to decrease with irradiation time. Decreasing the leaf temperature from 22 to 4 degrees C, at low light intensity, also induced a decrease in the F685/F730 ratio but an increase in the total fluorescence. Since photosystem I (PSI) contributes to the F730 emission band only, while photosystem II (PSII) contributes to both F685 and F730, the above evidences can be explained as due to the change with light intensity and temperature of quenching processes that affect more PSII than PSI.

Laser spectrofluorometry of agronomic plants in vivo at the single leaf level permits to investigate the effects of the growth phase, part, nodal position and age of the leaf, agrochemical treatment, external physical factors and plant diseases on the chlorophyll fluorescence. Such a spectroscopic approach can give the possibility to monitoring the development and health status of agronomic plants during ontogenesis and under different stresses. The relevant spectral wavelengths and criteria which correlate with status of the plant were determined.

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.

Photophysical properties of the widely used fluorescence tracers eosin, uranin and pyranine were determined in water at different pH. In order to elucidate the potential of LIF spectroscopy for in-situ measurements, calibration curves of uranin in different waters have been measured and the influence of other components in natural waters and of soil on the LIF signals was determined. Furthermore, LIF spectroscopy was applied to the investigation of sorption processes in water/soil-mixtures and of transport processes in soil columns.

Time-resolved emission spectra of humic substances of different origin have been recorded in order to extend our previous spectroscopic characterization of humic and fulvic acids in aqueous solution with stationary UV/Vis-absorption and fluorescence measurements. Instead of applying a fitting procedure, decay times are introduced as simple and robust experimental parameters for the quantitative description of fluorescence decays. The analysis of time-resolved emission spectra indicates a wavelength dependence of the fluorescence investigations of the interactions between pyrene and various humic substances in water. For all humic substances the quenching of pyrene fluorescence is dominated by a static quenching process, i.e. by a ground-state complexation. A significant influence of pH on the fluorescence quenching efficiencies is found, whereas no long-term changes of the interaction between pyrene and a humic substance are discernible. Time-resolved triplet- triplet absorption measurements reveal a decrease of chrysene triplet lifetime due to the presence of humic substances.

Extending our stationary fluorescence and absorption measurements of petroleum products in cyclohexane solution, time-resolved measurements of the fluorescence decay are presented in this paper. Several parameters suitable for the description of fluorescence decay curves of petroleum products are discussed in detail. Measurements of time- resolved emission spectra indicate an emission-wavelength dependence of the decay curves. We have found that the fluorescence emission of petroleum products is significantly influenced by oxygen. Applying a Stern-Volmer analysis it is possible to obtain Stern-Volmer constants K_sv and quenching constants k_q for the quenching of the petroleum product fluorescence by molecular oxygen. In addition, the excitation-wavelength dependence of stationary fluorescence as well as the concentration dependence of the effective extinction coefficients have been investigated.

An open path Fourier transform IR spectrometer and an ultra- violet differential optical absorption spectrometer were used during the 1996 Atlanta Olympics games to monitor for ambient ozone and its precursors near the Olympic Village. Both systems were operated continuously before, during, and after the increase in Atlanta's population associated with the Summer games. The study utilized the massive changes in population patterns to observe and measure changes in local air quality due to an increased local population. A second goal of the program was to evaluate both open path instruments in continuous field use over a period of several weeks. The evaluation included the following criteria: instrumentation operability, system precision and accuracy, detection capability, and over-all ease of use. Both open path systems selected and measured ambient levels of ozone. A limited number of ozone precursors were detected. The study was sponsored by the Georgia Institute of Technology's Air Quality Laboratory, the US Department of Energy, and the US Environmental Protection Agency.

An advanced monitoring station, equipped with a combination of DOAS system and classic monitoring devices, was set up in the urban background of Rome. An intercomparison between DOAS and gas-chromatographic technique for the measurement of the concentration level of benzene and toluene in the urban area has ben carried out. At the same time, an intercomparison between the DOAS and data provided by the chemiluminescent conventional analyzer has been developed to test the capability of DOAS system as a monitoring tool for secondary pollutants. The comparison between the data collected by the DOAS system and the conventional analyzer, provides quality assurance and reliability for the monitoring network and allows to understand the sources of the differences in instrumental responses. The results show that DOAS can be conveniently used for urban pollution monitoring.

The measurement of gas temperatures is important in many combustion, chemical manufacturing and materials processing applications. Different laser spectroscopic methods are applied to measure the temperature of gases. Nevertheless, up to now none of these methods have been calibrated against the international temperature scale of 1990. A transfer standard for laser thermometry has been developed to calibrate laser thermometry techniques. The standard provides optical access to a sample volume of a gas maintained at a stable temperature within the range of 300 K to 1850 K. The gas temperature is measured using built-in, calibrated thermometers including thermocouples. Accufiber optical-fiber probes and an optical pyrometer for traceability to the ITS-90. Broadband coherent anti-stokes raman scattering (CARS) and scanning CARS experiments have been performed inside the furnace. The measuring uncertainty of broadband CARS amounts to less than 4 percent between room temperature and 800 K. At temperatures between 800 K and 1850 K an uncertainty of less than 2 percent has been achieved. For scanning CARS the uncertainty and the precision amounts to 2 percent between 295 K and 1850 K.

Although much effort has been directed toward developing quality assurance/quality control procedures in open-path Fourier transform infrared (OP/FTIR) monitoring, many issues remain unresolved. Despite efforts in this area, there are still no universally accepted procedures for determining the accuracy and precision of OP/FTIR data. When the concentrations of atmospheric species are measured over a long, open path, several factors can influence accuracy and precision. In addition, broader issues, such as setting or determining data quality objectives for various types of programs, have not been discussed at all. Some aspects of these topics are presented in this paper.

Fourier transform infrared (FTIR) open path monitoring OPM is expected to work as a monitoring system for gaseous emissions and imissions within the open atmosphere. As such it is exposed to the dynamics of the atmosphere. Its methods, originating from laboratory spectroscopy, have to be adapted to the conditions of this specific operational area. Among other effects haze and fog influence the radiation transfer of the atmosphere and hence also FTIR- OPM. Model investigations have been performed to investigate the possible influence of haze and fog on common open path monitoring methods. These methods do not account for radiation emitted and scattered by the atmosphere.It is shown that the effects should not be neglected in certain wavelength bands under haze and fog conditions. As a result a new transmittance measurement method has been developed. It allows to completely cancel out the effects of emission and scattering of the transmitting medium. Furthermore it eliminates the influence of the spectrometer's inner radiation on the measured spectra, hence yielding pure transmittance spectra. From these then absorption coefficients can be derived and gas parameters like temperature and concentration. The method has been applied to determine the spectral transmittance of haze and fog and been compared to reference measurements.

As one part of a quality assurance in low-resolution FTIR spectrometry, the precision of a multicomponent monitoring system is studied. The instrumentation is composed of a commercial MIDAC M-2400-C FTIR spectrometer with a maximum optical path difference of 2 cm, a 22 m White cell, and a drier. Due to the difficulty to calibrate open-path measurements, a line-by-line calculation software, commonly used for high spectral resolution solar absorption spectrometry, was employed for the low-resolution horizontal-path measurements. Reference spectra of calibration gases recorded in the White cell are evaluated by both a partial-least-squares fitting method and the line- by-line analysis. Sources for the errors and their values differ in both methods. It is shown that the use of a line- by-line calculation software does not limit the efficiency but enhances the precision of the concentration analysis. Finally, the line-by-line evaluation yields relative errors between one and three percent for the gases CO₂, CH₄, N₂O, and CO.

Infrared Fourier transform open-path spectroscopy becomes a more and more well-known method to monitor air pollution. Several companies are even selling instruments especially devoted to this application. Numerous campaigns have delivered interesting information and proved the usefulness of the technique. However the results still suffer from a certain mistrust. Reliability, reproducibility, stability are for instance not yet well defined. In order to fill this lack, we have performed a set of test measurements which could be carried out on any FTIR long-path system. This quality assurance protocol includes the determination of noise, return signal stability, detection limits, precision and accuracy. The procedure to estimate each of these parameters is described. The feasibility and relevance of these measurements have been tested on both monostatic and bistatic set-ups. Both instruments have been studied over a period of several months. Many of the parameters can be calculated without doing extra measurements and were evaluated whenever the instruments were in use. To determine parameters such accuracy and precision, series of spectra were especially acquired. This shows the possibility to better quantify the performance of open-path FTIR spectrometers. Further improvements are also suggested.

A calibration experiment was performed by the Fachhochschule Duesseldorf in cooperation with the official calibration laboratory of the Environmental State Agency of Northrhine Westphalia. This was the first calibration of an OP-FTIR spectrometer at an official calibration laboratory in Germany. The calibration measurements were carried out along the standard ISO/DIS 9169, 'air quality - determination of performance characteristics of measurement methods'. A multipass cell with a light path of 20m was used. During these measurements the deviation between the calibration gas concentration and the measured concentration increased rapidly with higher concentration. This indicates a nonlinear calibration function of the OP-FTIR spectrometer used here and might be addressed to the used spectral resolution of 1.0 wavenumbers. The calibration measurements are still running for other gases and other OP-FTIR spectrometers.

The substantiation of the characteristics, which make the Open-Path FTIR technique attractive for monitoring the ambient air quality, is the aim of a validation program, which is realized at the Fachhochschule Duesseldorf. Part of this validation program are calibration measurement, which are important to determine the performance characteristics of a remote FTIR system. The measurements are carried out at the official calibration laboratory of the Environmental State Agency of Northrhine Westphalia and at the Laboratory for Environmental Measurement Techniques at the Fachhochschule Duesseldorf, using a high resolution Open- Path FTIR spectrometer combined with an adjustable gas cell from 7 to 110 meters. The calibrations were done for methane in a concentration range from 20 to 10000 ppm.m and are evaluated corresponding to the standardization documents which are currently used to determine the performance characteristics of continuous measurement systems. It turned out that the calculated calibration function for methane is nonlinear when analyzing by the classical least square algorithm. Furthermore, if using a nonlinear calibration function over the whole concentration range, the correction of measured concentrations and the calculation of the lower detection limits leads to unrealistic high values. Better results were achieved by separating the whole concentration range in a linear one at low concentrations and a nonlinear one at high concentrations in order to determine the characteristics of the used remote FTIR system.

A LIDAR is not only used for lIght detection and ranging, but nowadays it is one ofthe most powerful instruments for analysing the atmosphere. A lidarconsists of a transmitter and a receiver. The transmitter is sending a fairly collimated pulse or modulated beam of monochromatic laser light of a certain frequency into the atmosphere where this light is absorbed or scattered by the particles (molecules, water droplets, ice crystals, dust) of the atmosphere. The highly sensitive receiver records light which is reflected by the atmosphere within acertainfield of view(FOV) and with or without a certain state of polarisation. The transmitterand the receiver may be mounted atthe same place (then we calithe lidar monostatic) or they may be located in different places (then we call the lidar bistatic). Furthermore, the FOV may be directed along the same or different direction asthe (FOV of the) transmitted beam. Very often the FOVs of the transmitter and the receiver are coaxial cones; sometimes the receiver has several FOVs (e.g. a narrow central FOV and a ring shaped outer FOV) thus enabling recording of light of several states of polarisation (e.g. parallel and perpendicular to the direction of polarisation of the transmitted beam) simultaneously. Furthermore, some lidars are capable of transmitting and receiving light of severalfrequencies almost simultaneously. In addition to that some lidars provide a possibility of scanning the atmosphere. lidars may be ground-based, airborne or space-based. The primary goal of Iidar sensing is to acquire meteorologically important parameters of the atmosphere from the lidar signal. To be able to obtain such parameters, it is necessary to describe the lidar signal physically sufficiently precisely by a mathematical formula and to solve this formulaforthe interesting parameters. In this report the application for visibility detection is the object.

Wind profiles in the atmospheric boundary layer are a very important parameter also to study atmospheric exchange processes. The wind field in the atmospheric baundary layeris highly variable in spatial and temporal scales. For a few possible applications a more frequent wind sensing is necessary, i.e. - for airports located in low level jet areas, - for chemical plants to get information of the transport of toxic gases from leakages, - for meteorology in general to improve the weather forecast, - for environment protection purposes like dispersion studies. Only a few techniques can be applied to get the wind field in the boundary layer. Laser Doppler systems are candidates. LIDAR is an acronym for light detection and ranging, it is one of the most powerful instruments for analysing the atmosphere. A lidar consists of a transmitterand a receiver. The transmitter is sending a fairly collimated pulsed or modulated beam of monochromatic laserlight of acertain frequency into the atmosphere where this light is absorbed or scattered by the particles (molecules, water droplets, ice crystals, dust) of the atmosphere. The highly sensitive receiver records light which is reflected by the atmosphere within a certain field of view (FOV) and with or without a certain state of polarisation. The transmitter and the receiver may be mounted atthe same place (then we call the lidar monostatic) or they may be located in different places (then we call the lidar bistatic). Furthermore, the FOV may be directed alongthe sameordifferent direction asthe (FOVofthe)transmitted beam. Very often the FOVs of the transmitter and the receiver are coaxial cones; sometimes the receiver has several FOVs (e.g. a narrow central FOV and a ring shaped outer FOV) thus enabling recording of light of several states of polarisation (e.g. parallel and perpendicular to the direction of polarisation ofthe transmitted beam) simultaneously. Furthermore, some lidars are capable of transmitting and receiving light of 5everalfrequencies almost simultaneously. In addition to that some lidars provide a possibility of scanning the atmosphere. lidars may be ground-based, airborne or space-based. The primary goal of lidarsensing is to acquire meteorologically important parameters of the atmosphere fromthe lidarsignal. To be ableto obtain such parameters, it is necessary to describe the lidar signal physically sufficiently precisely by a mathematical formula and to solve this formula for the interesting parameters. In this report the application for wind detection is the object. This paper summarizes the principle technique, gives the special design parameters and presents test results. The requirements for the system are a compact design and an automatic or half-automatic operation.

The anticipated use of the FTIR remote sensing technique by personnel trained only at the technician level has prompted the US Environmental Protection Agency (USEPA) to pursue the production of a standardized procedure for instrument use. This procedure is to become one of a compendium of methods maintained by the USEPA. The compendium is a collection of methods for the measurement of toxic organic compounds and is commonly referred to as the to compendium. The procedure for the FTIR is number 16 and therefore is most often referenced as TO-16. The procedure begins by assuming that the operator is more or less familiar with the daily operation of the FTIR and has taken advantage of whatever training is available from the instrument manufacturer. The procedure further assumes that the quality assurance project plan for any one monitoring program has been followed and that the operator has in his possession a set of interferograms or single beam spectra from which concentration data is to be gleaned. There are two primary chapters in the document that describe how the spectra are to be processed in order to produce the concentration of various atmospheric gases. Chapter 8 presents the individual steps that all the spectra must be subjected to during the data reduction procedure. This chapter includes items for producing valid data such as correcting the spectra for line shifts and subtracting stray infrared energy. Chapter 9 describes the minimum requirements that are deemed necessary for quality assurance and quality control purposes.

The 'Commission of Air Pollution Prevention in VDI and DIN', which is officially responsible for the setting of written standards in the field of air pollution in Germany, has established a working group for standardization of open-path FTIR measurements in Germany. This group has presently worked out has worked out a draft for a VDI-guideline, in which it is laid down, how to perform measurements with the open-path FTIR to get reliable results.