The ceilometer LD-40 manufactured by Jenoptik Impulsphysik is an eye-safe lidar system measuring continuously under all possible climatic conditions and scanning the atmosphere up to the tropopause. It uses laser diodes with 855 nm wavelength that are pulsed at an average frequency of 4000 Hz. During the summer of 1998 the Meteorological Observatory Lindenberg run by the German Weather Service DWD was host to the measuring campaigns LITFASS and LACE. Two LD-40 ceilometers are in permanent operation at Lindenberg. Their measurements were compared with those of a research lidar system of the lidar remote sensing group of the German Max Planck Institute for Meteorology participating at LACE, and a star photometer run by the Meteorological Observatory Lindenberg. In particular, a data averaging method for detecting cirrus clouds is introduced, and a comparison is made between the optical thickness of the planetary boundary layer as detected by the star photometer and ceilometer backscatter data from heights between 70 m and 1200 m.

A novel backscattering lidar inversion procedure is presented. This method consists of two steps: the first one is the determination of a preliminary vertical profile of the unit volume extinction coefficient by the iterative Klett's method, and the second one is the determination of the vertical profile of unit volume backscattering coefficient from the previous step --using the relationship between (alpha) (r) and (beta) (r) -- which is given by two independent solutions for both variables. The calculation of the vertical profile of the 'lidar ratio' [determined as: (beta) (r)/(alpha) (r) is automatic ]. The proposed method is applied, in a preliminary case, to several backscatter lidar signals, obtained by a two wavelength backscattering lidar system in Greece. The proposed procedure can be applied for each wavelength of a multiwavelength backscattering lidar system, independently -- which means that the unit volume extinction and backscatterer profile of the atmosphere can be spectrally resolved. The general case of this procedure has not been applied yet, to a computer simulation, while this work is still in progress.

The LIDAR technique is an efficient tool for continuous monitoring of air pollution over urban areas, with high temporal and range resolution. The urban areas of Athens, Greece, exhibit high air pollution levels, especially those regarding suspended particulates, mainly linked with car traffic and industrial emissions. In this paper, we present the first mobile Greek LIDAR system, based on the LabVIEW code, now located at the Athens Technical University Campus, nearby the urban area of the city. The LIDAR dataset acquired, under various air pollution and meteorological conditions, gives specific indications of the diurnal variation of the backscattering coefficient and relative backscatter of the suspended particulates in the first 2500 - 3000 m ASL over the city of Athens. The LIDAR dataset acquired is analyzed in conjunction with meteorological data (temperature, humidity) and air pollution data (O₃ CO, NO_x), acquired at the same site, and conclusions are drawn.

The Greek Ministry of Environment (Department of Air Quality) launched in 1996 a number of projects aiming at the upgrading of its environmental services and authorities. One of these projects was about a LIDAR mobile station. The main scope of this project was the feasibility study concerning the application of a DIAL system in Athens geographical area suitable for monitoring the air pollution at places where corresponding environmental conventional instrumentation cannot be installed. The present paper highlights the major achievements of the above-mentioned LIDAR project. During the project period the available commercial LIDARs were evaluated and investigated about their capability to measure the required air pollutants by the Ministry. The project also dealt with the accuracy in the pollutant concentration and spatial resolution. The locations within Athens basin where the LIDAR can operate were spotted and a specific techno- economical study was carried out about the data transmission from the mobile station to the base. The project gave its recommendations (guidelines) about the suitable type of LIDAR to be used in Athens. It was also shown the possible scenarios of the financial management of the system, the purchase and annual maintenance costs of the system was estimated.

For the purpose of low tropospheric ozone and water vapor lidar measurements, a recent method, avoiding the high sensitivity to the inhomogeneous aerosols of the elastic DIAL, is offered by the Raman shifts of a single pump beam in the UV. In this work, we investigate the sensitivity of the method to both atmospheric and device perturbations by numerical simulation. The following effects have been modelled: inhomogeneous aerosol load, statistical error, deterioration due to cross-talk between the N₂ & O₂ Raman-shifted channels, deterioration due to intrusion of the elastically backscattered signal in the Raman-shifted signals, after-pulse noise.

A configuration of a UV ozone DIfferential Absorption Lidar (DIAL) based on a single cell filled with two Raman active gases has been developed. The cell is filled with a mixture of hydrogen and deuterium as active gases and argon as a buffer gas. The cell is pumped with the fourth harmonic of a Nd:YAG laser. The partial pressures of the gases are chosen to achieve even energy for the first Stokes of hydrogen (299 nm) and deuterium (289 nm), which are used as DIAL wavelengths. The ON and OFF beams, produced in this way, have identical spatial intensity distribution, identical temporal power profiles and the ability to probe the same air volume at the same time, which contributes to the decrease of systematic errors. Special care is taken to diminish the negative influence of the crosstalk between channels in the receiving part and the spatial nonuniformity of the receiving photosensors. Lidar measurements of tropospheric ozone concentration with vertical resolution ranging from 15 to 150 m and distances from 200 to 1200 m are performed. The results are compared with ground based punctual measurements and with DIAL measurements from a system with two Raman cells.

A new lidar for the measurement of tropospheric ozone is proposed, based on the differential analysis of the Raman backscattered signals on nitrogen and oxygen, which is far less sensitive to the aerosols than the classical DIAL system. Using a third Raman channel, the system is able to measure the water vapor mixing ratio simultaneously. The transmitting section of the instrument is composed of a single wavelength at 266 nm, generated by a quadrupled Nd:YAG laser, while the receiving section is the combination of a 20 cm Newton telescope, a polychromator, custom made band pass filters and miniature photomultiplier, giving a compact and efficient optical layout. The cross-talk between the different channels, and the rejection of the 266 nm wavelength have been measured in detail and will be presented. Time series of ozone and water vapor vertical profile during some days have been performed in the early spring 99.

Concentration measurements of trace gases in the atmosphere require the use of highly sensitive and precise techniques. The Fourier transform absorption spectroscopy technique is one of them heavily used for atmospheric measurements. It is currently used in all spectral regions, from the far-IR to the near-UV. The spectra recorded will be either fully resolved, showing well separated lines, or will only show absorption bands consisting of a great number of overlapping lines. The algorithm used to retrieve the concentrations of the atmospherically important molecules depends on this, as well as the resolution used to record the spectra. In both cases however, the instrumental function will modify the spectrum shape and has to be taken into account. In order to retrieve concentrations with the best possible accuracy, a thorough understanding of how the instrumental function affects line profiles or absorbances is essential.

A novel technique to measure trace gas concentrations is reported. It is based on a high finesse Fabry-Perot cavity, used as a gas cell, thus providing very long interaction path- lengths. As in Cavity-Ring-Down Spectroscopy, light absorption inside the cavity is detected, but measurements are performed in the frequency domain instead of the commonly used time domain. Moreover, wavelength modulation spectroscopy is performed for sensitive detection of absorption losses. Monitoring of water vapor near 1400 nm is demonstrated using this method.

Optical spectroscopic methods based on direct absorption offer a quantitative measurement of the absorbance, which is the product of the concentration, the molar absorption coefficient of the transition being observed and the length of the absorption path. An absorption sensitivity adequate for trace detection may be achieved by increasing the path length. One solution is offered by cavity ringdown spectroscopy (CRDS), attractive for its simplicity. We recently demonstrated that an external cavity diode laser (ECDL) can be conveniently employed for CRDS instead of a pulsed laser, contrary to previous applications. Here we extend this result to distributed feed-back (DFB) diode lasers. Paying special attention to the coupling of the laser source to the cavity, we developed an extremely simplified CRDS scheme with a sensitivity of about 10^-8/cm/(root)Hz. We then built detectors for methane and HF, working close to the optical wavelengths 1.65 and 1.31 micrometer, respectively With an optical assembly of about 50 cm length and a response time of about 1 s, these devices accurately measure atmospheric methane concentrations in the range 0.5 to 200 ppmv, and HF concentrations from 0.1 to 50 ppmv.

The spectral characteristics of a series of different VCSELs emitting at 850 nm and 762 nm have been examined, to assess the potential of this new kind of semiconductor laser for use in laser spectroscopy and fundamental metrology, particularly for environmental and energy monitoring of combustion processes. Adequate polarization control, which is necessary for laser spectral purity, was provided through manufacture of a dumbbell or 'figure-of-eight' shaped active region of the lasers at 850 nm. Spectral lineshape and linearity of the frequency tuning have been examined with a variety of methods such as optical interferometry and heterodyning. Optical heterodyning was used to measure a minimum linewidth of 90 MHz FWHM for a 762 nm VCSEL during single mode operation. Deviations from linearity of up to some GHz of frequency tuning with current were observed with an original application of a Twyman-Green interferometer, with basic current tuning rates of 58 GHz/mA and 130 GHz/mA for an 850 nm and a 762 nm VCSEL, respectively. The frequency stability for a 762 nm device was measured to be approximately plus or minus 40 MHz. A possible problem for the use of VCSELs in wavelength modulation spectroscopy (WMS) is that due to their extremely high tuning rate with current: ultra-low noise current drivers must be used in order to achieve high sensitivity detection. The WMS absorption spectrum with VCSEL of a number of lines of the oxygen molecule at 760 nm have been registered and studied.

In order to better understand the chemistry and the transport mechanisms in the lower troposphere, a new original technique has been developed and tested. The experiment consists in recording high resolution infrared solar absorption spectra containing signatures of important atmospheric constituents, simultaneously from the International Scientific Station of the Jungfraujoch in Switzerland [ISSJ, 3580 m a.s.l., 46.5 degrees N, 8 degrees E, Bruker 120 HR Fourier transform spectrometer (FTS)] and from a nearby valley (Grindelwald, 1070 m a.s.l., Bruker 120 M FTS). Analysis of individual spectra allows to determine vertical column abundances: differences between measurements at ISSJ and at Grindelwald enable us to retrieve the constituents' concentrations between 1070 m and 3580 m, assuming a constant volume mixing ratio in this layer. A first measurement campaign has been organized during the months of May and June 1998. After an initial period of instrument intercomparison at ISSJ, the mobile instrument was moved down in the valley and installed for one month in Grindelwald. When operated side by side at the Jungfraujoch, measurements made by both instruments showed a very good agreement (maximum bias of 1.5%). Analysis of spectra recorded synchronously at the Jungfraujoch and at Grindelwald gave average boundary layer concentrations for a selected set of tropospheric molecules, i.e. methane, nitrous oxide, carbon monoxide and ethane. Comparison with other results and with carbon monoxide in-situ measurements made at ISSJ showed a good agreement.

A fast tunable diode laser sensor has been applied for micrometeorological flux measurement of methane emissions from rice paddy fields in order to assess the quality of data on methane fluxes and allow a comparison with simultaneously recorded data provided by the closed chamber method. Systematic differences between chamber and the eddy correlation technique have been found and it seems that chamber measurements over estimate the actual emission up to 70%. This finding demonstrates once more that TDLAS is a valuable tool for atmospheric research and quality assurance.

Tunable mid-infrared radiation in the spectral range between 6.8 micrometer and 12.5 micrometer is generated via nonlinear optical difference-frequency-generation in AgGaS₂. The input radiation that is needed for this process is provided by two high-power single mode diode-lasers. The combination of this MIR-laser source with a MIR-detector and lock-in detection technique has very interesting applications in spectroscopy. The on-line performance of this MIR-spectrometer is shown as single rotational lines of molecules are probed in the gas phase and in the vapor extracted from contaminated soil samples.

The Global Ozone Monitoring Experiment (GOME) is a new atmospheric chemistry instrument on-board the ERS-2 satellite which was launched in April 1995. The GOME is designed to measure a range of atmospheric trace constituents, with particular emphasis on global ozone distributions. We show that atmospheric UV/visible backscatter spectra obtained by the GOME spectrometer may be used to retrieve column amounts of key trace species associated with smoke cloud combustion from biomass burning events. We focus on the severe rain forest burning in SE Asia from August to October 1997. The current operational GOME Data Processor (GDP) was used to retrieve column distributions of NO₂ and CH₂O in and around the smoke-polluted region. For ground scenes with low cloudiness, the differential optical absorption spectroscopy technique (DOAS) applied to backscatter spectra yields column distributions of NO₂ and CH₂O in and around the smoke- polluted region. An increase by almost a factor of two of the vertical NO₂ content in the tropical atmosphere is apparent over a large area within the smoke cloud; this clearly indicates the ability of GOME to measure tropospheric NO₂ content. CH₂O is detected only in areas closest to combustion sources and the detected slant column amounts correspond with previous estimations of vertical column amounts of CH₂O for biomass savannah burning.

The methodology of evaluating the exchange rates of CO₂ and water vapor between vegetation and the atmosphere is presented. The two gases are measured with a short open path, fast responding infrared absorption gas analyzer. To determine the turbulent fluxes due to large scale eddies, high resolution wind measurements are obtained with a five-hole pressure sonde and a fast GPS (Global Positioning System) receiver. Measurements taken over Monte Bodone near Trento, Italy, a plateau in the Alps, are evaluated. The CO₂ and water vapor budgets for the air layer above a few square kilometers were calculated and exchange rates for H₂O and CO₂ with the vegetation were estimated.

Most satellite measurements of atmosphere related quantities and parameters come from passive instrumentation, that provides huge amounts of data for global scale atmospheric analysis with quite limited spatial resolution. When higher resolution is desired, ground based systems are opportunely exploited. The increasing use of satellites pushes the research towards the realization of systems, based both on spaceborne and ground instrumentation, designed to exploit attenuation measurements at the infrared. The distribution of atmospheric molecular components can be retrieved from such measurements through ad-hoc tomographic processing. In this paper we describe a methodology that allows attenuation measurements at infrared to estimate mean concentrations of atmospheric molecular components along quasi-vertical rectilinear paths. A number of ground passive infrared stations is needed, distributed along a baseline in the area of interest, and spaceborne monochromatic infrared sources. Measurements made along all rectilinear paths defined by each satellite pass above the site, are processed following an ad hoc tomographic inversion technique to provide the 2D vertical distribution of the atmospheric molecular components of interest. Some simulation results are presented to demonstrate the applicability of the cited tomographic technique. Carbon Monoxide has been considered as the molecular test species in the simulations, based on standard atmospheric models.

Infrared spectral features of organic hydrocarbons were investigated with respect to single compounds. A separation and consequently a quantitative concentration determination is possible for ethane, ethene, ethyne, propene, iso-butene, benzene, toluene, o-xylene, m-xylene and p-xylene using a MCT detector with a cut-off frequency below 660 cm^-1. The spectral features of propane, butane, pentane and hexane cannot be separated. In order to be able to derive parameters, such as detection limits, accuracy, precision and the influence of interfering species or different reference data, validation measurements were carried out in a road tunnel and in the laboratory using an open White mirror compartment and closed White cells. FTIR spectra were collected with two spectrometers at different spectral resolutions. Parallel GC measurements were made for comparison.

Atmospheric particle pollution and particles emitted by industrial plants are extremely dangerous for human health. Indeed, they have diameters in such a range (approximately 0.1 - 5 micrometer) that they can penetrate our respiratory system, but cannot be expelled during exhalation. Therefore, it is extremely important to detect them and characterize their size distribution. In this paper we propose the use of a novel instrument recently developed by the authors for the monitoring of airborne particulate at concentration levels so to comply with the current European Economic Community (EEC) regulations. The instrument is based on spectral extinction measurements over long optical paths and is able to recover, almost in real time, both concentration and size distribution of particles with diameters in the range of interest. The sensitivity and accuracy of the instrument were estimated by means of measurements in a clean room and by using calibrated particles dispersed in water. Our results show that, by carrying out measurements over optical paths of approximately$DAL100m, the instrument is able to detect concentration levels well below the ECC limit imposed for the atmospheric pollution. Scaled over shorter optical paths (approximately 10 m), the limit imposed for particle emissions by industrial plants can also be detected very accurately.

A modified mid-size low by-pass aero-engine running on a sea level test bed was used for measurements with non-intrusive demonstrator systems and currently used gas sampling analysis techniques. A novel open-path White mirror system was developed and installed in the test bed to enhance the sensitivity of non-intrusive FTIR spectrometry. A comparison was made of the different measurement techniques at several engine thrust levels i.e. gas concentrations. This included the emission and absorption mode of the FTIR-spectrometers with the multi-path reflection compartment as well as the single emission mode. A new calibration procedure with a hot cell filled with CO (temperatures 300 to 750 K) was developed and used to calibrate the FTIR instruments. Retrieval results from FTIR measurements were obtained by using a rectangular and Gaussian distribution profile of temperature and gas concentrations in the plume. The FTIR measurement results for CO₂, CO, and NO have been proven to be in agreement with the intrusive data. The deviations were generally in the order of plus or minus 30%, i.e. comparable to the day-to-day variations of the engine emissions. NO₂ could be detected in the absorption mode only.

Fourier Transform Infrared (FTIR) spectroscopy was used to investigate the IR spectral absorption of soot particles from a Palas smoke generator. A TSI Condensation Particle Counter was used to quantify the number of soot particles produced and this was related to the intensity of the IR absorption. The broad band IR absorption increases with soot particle count but quantitative measurements of total soot mass were not obtained because accurate size distributions of the particles were not available. A sample of gas turbine engine exhaust gas was analyzed by Gas Chromatography-Mass Spectroscopy to determine the primary constituent unburnt hydrocarbon (UHC) species. Their relative proportions were measured with a Flame Ionization Detector (FID). These species are predominantly unsaturated C2 to C6 hydrocarbons. The infrared absorption spectrum of the exhaust gas sample was compared with that of combustion products from a laboratory kerosene burner using a multipass White cell. These were also compared with reference spectra and IR spectra of UHCs obtained non-intrusively from gas turbine engine tests. There are IR spectral band shape differences indicating that the relative proportions of the constituent UHCs in gas turbine exhaust are different from those in a kerosene burner plume.

Laser Induced Incandescence (LII) has been demonstrated as a non-intrusive technique for measurement of particle concentration in the exhausts of aero-engines on sea level test beds as part of a European Union collaborative program (AEROJET) aimed at replacing gas sampling rakes behind development engines with non-intrusive instrumentation. Currently emissions of CO, NO_x, unburned hydrocarbon, and smoke from aero-engines must be shown to be less than internationally specified limits. Measurements are made on development engines on sea level test beds by applying a number of standard analytical methods to extracted exhaust gas samples. The hardware required for exhaust gas sampling is heavy and complex and is expensive to build and install. As a result, only the minimum number of emissions tests are conducted during an engine development program, and emissions data is only available to combustion engineers late in the program. Hence, there is a need for more versatile and less costly non-intrusive measurement techniques. Molecular species can be measured using Fourier Transform Infrared (FTIR) spectroscopy, while LII is a promising smoke measuring technique. The development of an LII system specifically designed for exhaust applications is described.

Multi-path reflection mirror systems in White- or Herriott- type configuration have been widely used to enhance the absorption path-length and thus the sensitivity of laboratory spectroscopic systems, e.g. for smog chamber studies and molecular spectroscopy. Field studies, for instance using mobile tunable diode laser spectroscopy have widened the range of applications of these mirror systems for specific measurement tasks. In this paper a special designed White-type system mounted in two racks with 5 m base-length and adjustable optical path-length up to 74 passes is described. This system has been tested and successfully used to enhance the sensitivity of non-intrusive FT-IR measurements of aircraft engine exhaust emissions in the harsh environment of an engine test bed. The open cell around the engine plume including the transfer optics for the adaption of the spectrometers in a separate room allowed manual switching between passive FT-IR emission measurements, FT-IR absorption measurements with the cell, and, by covering the infrared source (globar) with a shutter, multi-path FT-IR emission measurements. Tests prior to the aircraft engine measurements were made to investigate the influence of different path- lengths, the position of the plume in the White cell, soot in the exhaust gas, and vibrations of the mirrors. The FT-IR spectra from all three measurement modes using the White cell during the engine measurements were found to be of good quality and the results of the analyses were comparable to the results from intrusive measurement systems.

The ENEA mobile fluorosensor laboratory has participated to the XIII Italian Antarctic Mission operating in the oceanographic campaign (R/V Italica, Nov. '97 - Jan. '98). Sea water quality parameters (phytoplankton and yellow matter concentration, turbidity and biomass productivity) have been remotely and in situ monitored during the cruise in the Ross sea and along the Southern Ocean transects up-to New Zealand. Georeferenced data have been collected and released on thematic maps. Algal blooms and temporal variations of the monitored quantities have been reported. Chlorophyll-a fluorescence intensities have been compared with laboratory determinations, the absolute values of conversion factors in have been calculated for spectrofluometric and lidar data.

Seawaters detailed spectroscopic analyses were carried out in the ENEA mobile fluorosensor laboratory participating to the oceanographic campaign within the XIII Italian Antarctic Mission (R/V Italica, Nov. '97 - Jan '98). A complete set of in-vivo emission and excitation spectra was measured during cruises in the Ross Sea and along Southern Ocean transects up- to New Zealand. Measurements allowed for distinguishing among natural seawater components (tyrosine and tryptophan protein- like substances) and for identifying phytoplankton pigments (Chl-a, b, c, carotenoids, phycoerithrin, and phaeopigments). Georeferenced data have been collected at fixed time intervals and released on thematic maps.

In the paper, the possibilities of classic and laser fluorimetry in photosynthesizing organisms (PSO) diagnostics are analyzed. Some special features of fluorescence of PSO excited by laser pulses are discussed. The results of research presented in the paper refer to the water PSO -- phytoplankton. However, some of them are valid for vegetation. Methods of linear and non-linear fluorimetry make it possible to determine the following parameters. (a) Fluorescence parameter (Phi) _o equals N_fl^o/N_RS, where N_fl^o is the photons number of photosynthesizing organism fluorescence without saturation effect, N_RS is the number of Raman scattering photons from water molecules. (b) Parameter of photosynthetic activity (eta) equals F_v/F_m, where F_v and F_m are the intensities of variable and maximum fluorescence response. This parameter can be determined by the pump-and-probe technique. (c) Excitation cross-section of fluorophor (sigma) . This parameter depends on energy transfer form auxiliary pigments and reflects the group and species composition of algae. The cross-section (sigma) and other photophysical parameters of PSO can be determined by non-linear saturation spectroscopy. In principle, these parameters can be used for the diagnostics of PSO, i.e. for the determination of chlorophyll-a concentration, of photosynthesis efficiency and of phytoplankton species composition. In the paper the examples of spatial distributions of parameters (Phi) _o, N_fl^o and (eta) obtained by ship lidar and by submersible biophysical probe are represented. The results obtained in some sea expeditions using lidars and double-flash submersible fluorimeter for phytoplankton diagnostics, are briefly analyzed.

Optical remote sensing of ocean color is a well-established technique. But most algorithms developed hitherto have been based on the assumption that only the phytoplankton affect the optical properties of the ocean. Such algorithms are often based on assumptions that become questionable in coastal areas. The assumption of a near-infrared dark pixel in the satellite image, will no longer be valid, and the band-ratio technique used for computing the algae concentration will also become inaccurate. To overcome these limitations we have developed an inverse-modeling algorithm for retrieval of marine constituents. Here the determination of ocean color is based on a three-component optical model consisting of chlorophyll-a, suspended matter, and yellow substance. We also use one parameter to describe the thickness of the aerosol layer. A simulated-annealing optimization scheme is employed to minimize the difference between measured satellite data and corresponding simulated data obtained using a coupled atmosphere-ocean radiative transfer code. The same optimization method has also been applied to the problem of retrieving the algae concentration in waters with vertical structure. In this case the marine parameters of interest are the algae concentration in two different layers as well as the thickness of the first layer.

In this article we consider laboratory measurements of scattering by algae. We investigated the optical properties of a culture of the chlorophyte Chlamydomonas vectensis over almost two division cycles. The cell culture was synchronized which means that all cells were at the same stage in the growth cycle and thus divided at approximately the same time. By measuring the scattering properties of the synchronous culture during the full growth cycle, we get information about the influence of size changes of the individual cells as well as changes in the cell concentration. We measured of the scattering phase function in the interval from 1.7 degrees to 7.7 degrees at a wavelength of 633 nm using a CCD camera from Astrocam. In addition we measured the scattering phase function at 90 degrees, including the degree of polarization. We checked the experimental setup by doing a similar experiment in which we used monosized spheres from 'Dyno Particles AS,' so that the results can be compared with Mie calculations. The absorption and attenuation coefficients were measured by an AC9 instrument from WetLabs. The cell size was measured with a Coulter Counter, and the concentration was determined using a microscope. As expected, the optical properties were strongly dependent on the concentration of cells. Furthermore the shape of the scattering phase function and the degree of polarization were seen to depend not only on the concentration but also on the time of day.

Solar radiation is the energy source for all photosynthetic life-forms. Due to their individual pigment compositions only a specific part of the spectrum can be used by the single species for photosynthesis. Therefore multispectral radiation measurements are helpful for their investigation and monitoring. With the background of increasing ultraviolet radiation due to the decreasing ozone layer in the atmosphere, the measurement of the UV-A and UV-B part of the spectrum is of increasing interest to people. In the RAMSES project (Radiation Measurement Sensor with Enhanced Spectral resolution), founded by the German Ministry of Research and Technology, a new subminiature multispectral radiometer is under development. This new instrument allows spectral measurements in the range from 250 to 720 nm. A modular concept of the instrument, combined with very low power consumption, allows to use the instrument in profiling systems as well as in stand-alone applications, such as moorings, monitoring systems or weather stations. Sensor heads with different detection characteristics are available, and up to 16 of them can be combined to a single instrument for simultaneous measurement, e.g. for up-welling and down-welling light. Typical applications of this instrument are satellite calibration and validation, UV measurements, biology, ecosystem modelling, water quality and even climatology.

A photosedimentation method for floc characterization was developed combining gravitational settling with photoelectric measurements. Settling particles cross a light beam that illuminates a detection system. The attenuation of the beam is related to the projected area of the particles and so the particle size distribution can be determined. When a floc crosses the beam the amount of light reaching the detector is reduced.The signal from the detection system is sent to the data acquisition system. Voltage/time signals are analyzed in order to produce the physical characteristics of flocs. Different detection systems were tested with a single or a double photodiode. Calibration tests were performed with glass beads of known physical characteristics and kaolin and silica suspensions were used for simulation tests. different experimental conditions of floc formation (mixing conditions and polymer concentration) were changed and the corresponding floc characteristics were calculated.

The concept of waste water treatment from microelectronics fab processes is referring to waste water discharged from ultrapure water plant which can't be treated on recovery waste water section. These wastes concentrated contains organic and inorganic acids, alkalis, metals, cyanide, chromium and fluoride effluent from fab processes. They will be canalized on qualities for treatment sections which permit the discharge of treated waste water as neutral with solids removal as compacted sludge. For management of waste water treatment plant we are using the fiber optic sensors as follows: level and flow control, signalization automatic pumps control and protection, solid control, leak detection a.s.o. The neutral quality of treated water has 'null' impact against of environmental system recommended for all semiconductors and microelectronics fab processes.

In order to demonstrate the possibility of performing direct absorption spectroscopy of Hexavalent Chromium aqueous solutions, absorption measurements were performed at the dual- beam spectrophotometer in the 250 - 850 nm spectral range, with 10 mm and 100 mm path lengths. Low concentration (26 - 520 (mu) g/l) (and high concentration (2.6 - 52 mg/l) solutions were analyzed, showing that it is possible to implement a basic instrumentation for risk condition monitoring and a more advanced instrumentation for quantitative measurements.

For the first time the herbicides ethidimuron, amizol and methabenzthiazuron were detected in water by means of time resolved laser fluorescence spectroscopy. The suitability of the algae chlorella kessleri as a biological indicator was tested. By using time resolved LIF, the herbicides' absorption spectra and their effects on the fluorescence properties of the algae it was possible to distinguish between the three herbicides.

We introduce a fiber optical sensor which is capable of analyzing polycyclic aromatic hydrocarbons (PAHs) and monoaromatics like benzene, toluene, xylene, and ethylbenzene (BTXE) in natural water samples. The compact system is based on laser-induced, time-resolved fluorescence emission spectroscopy. It uses a miniaturized all solid state laser which can be operated at 266 nm and 355 nm. The 3-D data set of a time-resolved fluorescence spectrum is reduced to a 2-D data set by a factor based technique, i.e. by dividing the raw data by a decay matrix with exponential decay profiles. The resulting data have a 2-D spectral format but still contain the temporal information. With these data a partial least squares regression has been carried out and optimized for a quantitative evaluation of the data. After the calibration xylene could be selectively analyzed in the 0 - 200 ppb range with a prediction error of 15 ppb. The PAH calibration was able to predict the concentration of 9 out of 15 EPA PAHs with errors between 0.07 (mu) g/l (benzo[a]pyrene) and 1.6 (mu) g/l (anthracene, naphthalene).

The objective of this investigation was to develop a fast method for the in-situ characterization of chemicals solved in water based on Coherent Antistokes Raman Scattering (CARS). In order to test the potential of CARS as a tool for the in-situ spectroscopy scanning and multiplex CARS techniques were investigated. Polarization CARS (PCARS) was used to reduce the nonvibrational resonant signal generated by the electron cloud of the solvent molecules. The spectra of some alcohols and pollutants such as pyridine, nitrate and sulfate were investigated. Computer simulations were applied for the evaluation of the CARS spectra. The most evident advantage of CARS in comparison with other Raman methods is the very short time to achieve a spectrum. The shortest time to get a spectrum is limited by the length of the laser pulse (e.g. 5 ns). In addition no sample preparation is necessary.

Weather satellites play a key role in modern meteorology and give an undoubted contribution to a correct weather forecast. Image sequences transmitted by geostationary satellites like METEOSAT permit to track the temporal evolution of typical clouds structures (vortices, fronts) associated to depression phenomena. A fully automated system for clouds tracking is an important challenge to image processing applied to meteorology. This paper proposes an enhancement of modal matching techniques as a more suitable alternative to optical flow-based or parametrical methods. Modal matching permits a robust point-feature association among strongly deformed shapes, as well as a highly detailed description of complex shapes. Modal expansions of virtual elastic bodies associated to the shapes provide coarse-to-fine descriptions of them: pairing homologous low frequency modes and discarding noise and sampling error affected high frequency ones gives a robust basis for vibration-based point correspondence. The classical technique requires dense sampling for strong modes similarity: this paper tackles the problem of compensating the degenerative effects of low sampling by efficiently controlling modes pairing and by forcing the locality constraint through balls tracking the contours: since mismatch probability is higher in particular localized areas, balls actually work as a shield, letting modal match perform reliably inside them.

The paper summaries the results of laboratory and field experiments during August 1991, September 1997 and 1998 along the Russian coast of the Black Sea. The main objects of investigation were aquatic humic substances, dissolved protein-like molecules (free and combined amino acids) and petroleum hydrocarbons in dissolved-emulsified state in the water column. Spectral luminescence characteristics of various water samples were investigated using laser spectrometers with excitation wavelengths 266 and 337 nm and lamp fluorescence spectrometers. Relying on these results we briefly review the opportunity of the method when the wavelength of exciting radiation is located in the range of 310...400 nm. We also discuss advantages of fluorescence spectroscopy with the use of the more informative range of exciting radiation: 230...310 nm. Only in this case the spectrum of natural water contains a protein fluorescence band in addition to humic matter and petroleum hydrocarbon fluorescent responses. The procedure and the result of computer decomposition of natural water spectra into basic contributions are presented in the paper. This information can be used for in situ measurements of fluorescence signals as well as for determination of organic matter concentrations.

The concept of a system for continuous express monitoring of coastal sea water areas is presented. According to the suggested concept, the monitoring system should consist, in general, of three parts, in which the key role should belong to laser devices: (1) shore-based lidar that performs continuous monitoring of water surface and sub-surface layer of water (and, possibly, of atmosphere) in the selected water area; (2) patrol boat equipped with submerged portable devices, including laser spectrometer with submerged optical fiber probe; (3) coastal laboratory equipped with devices for detailed (but express enough) analysis of water samples, specially chosen by the results of remote laser sensing and submerged device data. Some features of remote sensing by means of shore-based lidar are considered. The main feature is sliding incidence of laser beam to water surface. The coastal sea waters have much more complex and variable composition than open sea water. The possibilities of different versions of laser fluorimetry in diagnostics of organic compounds in coastal sea waters are analyzed.

A submarine fluorescence lidar has been developed for the detection of hazardous chemicals on the seafloor of the German Bight. Signals are dependent on the inherent optical properties of the seawater column, the seabed and the substance properties, mainly their absorption coefficient, volume scattering function, fluorescence quantum yield and reflectance. Although the instrument is designed to inspect the seafloor it allows to record time-resolved spectra in order to derive information about the water column. Interpretation of these data is normally done with the classical lidar equation which is based on several simplifying assumptions. In its conventional analytical form multiple scattering is not considered. This leads to an increase in signal intensity and to optical ringing. Additionally, fluorescence lifetimes and detector response function may result in an uncertainty of distance determination. Monte Carlo simulations were done to analyze the performance of the submarine fluorescence lidar for realistic scenarios. Results are compared with theoretical predictions of the lidar equation. It is shown that the error in signal intensity increases with the turbidity whereas the slope of the lidar curve appears to be independent of it. Depth-resolved measurements are not limited by the penetration depth of the light but by multiple scattering effects.

Sunken objects at sea such as lost ship cargo are often not detectable by conventional video cameras because of their low contrast due to the high turbidity of the water column. A well-known contrast enhancing imaging technique in turbid media is range gated video recording. 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 that increases the visibility range in turbid water up to eight attenuation lengths. Furthermore, image reconstruction algorithms can be applied if the modulation transfer function of the water column is known. However, these approaches only lead to an increase in visibility of a target if the intensity of light scattered by the seafloor differs from signals that originate from the object under investigation. Conventional monochrome video cameras as well as rang gated systems record the intensity of light, whereas its spectral composition and polarization characteristics are not considered. A linear polarized monochromatic illumination source and suitable cut-off and polarization filters in front of the camera allow to record the fluorescence images and to detect the degree of depolarization which is a function of the roughness of the scattering surface. This can result in a better contrast between target and seafloor. A prototype of a submarine imaging instrument has been realized for operation in the German Bight that makes use of techniques described above. Results of tank trials are presented.

In summer 1998 a measurement campaign was performed at the lake Baldeney See in the south of the city of Essen in Germany. Two major goals should be achieved: First the intercomparison of several different remote sensing systems in real field measurements and second the determination of the ozone levels during summer with respect to the complex orographic and climatological situation of the lake Baldeney See which is intensely used as a recreational area. This paper refers to the results of the intercomparison of the remote sensing systems open-path FTIR, DOAS and TDL and presents a new automatic background generation routine for analyzing the FTIR spectra.

The demand of instrumentation in the field of remote sensing is increasing rapidly. For international compatibility, for reliable results and precise long-term investigation, necessary for example in the measurement of climatic trends, accurate traceability of the results to international standards or SI-units is mandatory. Additionally, interpretation of the results strongly requires a careful evaluation of the involved errors and the resulting uncertainties in order to allow for a rating of the obtained results. For that purpose quality assurance was introduced, not only for industrial fabrication, but also, and with increasing tendency, for industrial and scientific research. As an overview, the necessity and the possibilities of quality assurance in the area of remote sensing are discussed. Taking remote sensing of temperature as an example, the general approach is described. For that purpose, a description of heatpipe blackbodies used as standard radiation sources and of the apparatus for measuring the area of the beam limiting apertures is given. We also introduce the applied mathematical model for determination of the emissivity of the blackbodies, which crucially influenced the detected radiation temperature and the uncertainty. Finally the evaluation procedure of the uncertainties is described and a sophisticated estimation of the overall uncertainty is presented.

Spectrally high-resolved infrared spectra from Fourier transform experiments are often used to determine atmospheric parameters. Reliability of results depends on the quality of the measured spectra and on the successful fit of modeled spectra to the measured ones. Algorithms are presented which enable automated quality control of measured spectra as well as the differences between measured and the calculated spectra, so-called residual spectra. The measured scene spectrum is checked for successful phase correction, the compliance of given maximum and minimum envelope functions, spectral patterns in the variance spectrum, which is calculated during coaddition of several spectra, if applicable. The symmetry of isolated lines, the consistence of expected and real noise, and the plausibility of the magnitude of background radiation are assessed. The quality of the spectral fit first is assessed by means of the X²-test and, is checked for superimposed functions, periodicities, spectral signatures, and conspicuous determine possible calculated spectra.

The capability of taking non-intrusive species measurements in a jet plume of a modified mid-size low by-pass aero-engine running on a sea level test bed at several thrust levels was demonstrated. Also conventional intrusive measurements were performed with a spatially resolved method using a traversing single-point sampling probe which fulfills ICAO standards. The FTIR spectrometry measurements included both emission and absorption mode with a multi-path reflection compartment as well as the single emission mode. Due to the lack of a common/unique definition for the exhaust plume diameter it was found that the column density was the best measure to compare the different techniques. The FTIR engine measurement results for CO₂, CO, and NO have been proven to be in agreement with the intrusive data within plus or minus 30%. Several error sources during the radiometric radiance calibration were identified which lead to uncertainties in the FTIR retrievals, namely (1) incomplete knowledge of the optical surface emissivities, (2) incomplete knowledge and inhomogeneities of the optical surface temperature, and (3) undefined instrumental drifts and non-linearities during the calibration.

To carry out metrological tests on the automatic devices used in air quality monitoring networks, INERIS follows a standard text. In order to apply it, the instruments have been fed with reference mixtures of gases in several reproducible concentrations. Compliance with this requirement is quite easy to obtain, in the case of conventional techniques, but the problems remain with optical remote sensing instruments. The difficulties can be solved by using the Beer-Lambert law indicating that the product of the concentration by the distance is a constant value. To implement this optical law, INERIS uses a system with a two meters glass cell with quartz windows inserted in the instrument beam and fed dynamically with known concentrations of reference mixtures of gases. The test-bench facility is set up in a tunnel 90 meters long in INERIS. Tests on SO₂, NO₂ and O₃ were carried out in 1997 on two types of DOAS systems set up in parallel: an OPSIS system and an Environment SA SANOA system. The following features were tested: the detection limit, the linearity and the drift. The tests results on the response of the two types of instruments are in agreement with the results obtained by the ERLAP at the Joint Research Center in Ispra.

Methods which are in discussion to enter a VDI guideline will be presented. Examples of application in local scale area selected. The VDI 'Richtlinie VDI 3786 Umweltmeteorologie,' is divided in many parts. Part 15 shows the remote sensing methods for visibility measurements, part 14 describes the wind profile measurements. Wind profiles in the atmospheric boundary layer yield a very important contribution also to the investigation of atmospheric exchange processes. The wind field in the atmospheric boundary layer is highly variable in spatial and temporal scales. For a few applications a more frequent wind sensing is necessary, i.e. (1) on airports located in low level jet areas, (2) near chemical plants to get information of the transport of toxic gases from leakages,(3) for meteorology in general to improve the weather forecast, (4) for environment protection purposes like dispersion studies. The following statements are valid for visibility measurements: (1) Lidar can provide the same information of the visibility as conventional sensors, but in addition lidar will provide range resolved measurements. (2) It is possible to shrink a lidar down to the size of binoculars. (3) It is possible to measure local visibility with an eye-safe (class 1) lidar. (4) Layers can be detected up to 250 m distance in approximately 2 s even with a small size instrument.

The OP-FTIR measurement technique and other remote sensing systems (for example UV-DOAS and TDL) become more and more established methods to monitor the ambient air quality. Some quality assurance procedures have to be done on the field measurement data to get more reliable results. Both the German and US-EPA standardization documents for the OP-FTIR technique prescribe such procedures to check the data. To assess the applicability of these procedures, OP-FTIR field measurement data of a three month continuous measurement campaign were evaluated concerning the signal strength, the influence of stray light, water vapor concentration, baseline noise, wave number shifts and the detection limits. In addition the long time signal stability of the OP-FTIR systems and the UV-DOAS systems are intercompared. The results of the several quality assurance procedures will be presented in this paper.

The central problem in laser sensing of natural organic complexes (NOC) in water, is their identification and determination of their state. This is an essential condition for quantitative characterization of an object by optical methods (e.g. fluorimetry). It is very difficult to solve the NOC identification problem dealing only with spectra. It is necessary to penetrate to the molecular level, and to supplement spectral data with molecular photophysical parameters (absorption and fluorescence cross sections, rates of intermolecular transitions and of intermolecular excitation-energy transfer, etc.). Furthermore, it is necessary to measure these parameters in vivo and in situ, under conditions of absence of accurate a priori data. This can be done only by non-linear laser fluorimetry. In this paper, the results of computer experiments and real experiments, illustrating capabilities of non-linear laser fluorimetry in diagnostics of NOC, are presented. To solve the inverse problem, the method of artificial neural networks was used. it is shown that it is possible to achieve the determination precision of the photophysical parameters not worse than the measurement precision of the saturation curve, using a few-parametric model of the formation process of the NOC fluorescence response at pulse laser excitation, and taking into account NOC specifics.

Fluorescence of organic admixtures in water and atmosphere is the main information source for express diagnostics of the environment. A quarter of century ago it was proposed to normalize fluorescence intensity to the intensity of Raman scattering by molecules of the main component of medium (water in water medium, nitrogen in atmosphere) and to measure the normalized fluorescent parameter (Phi) _O equals I_fl^O/I_RS, where I_fl^O is fluorescence intensity (or number of photons) of the admixture in absence of saturation, I_RS is the intensity (or number of photons) of the Raman scattering by water (or nitrogen) molecules. In fact, the parameter (Phi) _O is the fluorescent signal from unit volume (of water or atmosphere) normalized to the intensity of exciting optical radiation. Some requirements being fulfilled, the parameter (Phi) _O is a linear measure of concentration of the admixture, independent of characteristics of medium and device, therefore, it can be proposed as a standardized parameter in fluorescent diagnostics of organic admixtures. These requirements are analyzed in this paper. The stability and controllability of some parameters which determine the value of the coefficient (alpha) in the formula C equals (alpha) (Phi) _O (where C is the admixture concentration) are discussed in this paper. These parameters are: (1) relative dispersion of the attenuation index (Delta) (epsilon) /(epsilon) , where (Delta) (epsilon) equals (epsilon) ((lambda) _fl)-(epsilon) ((lambda) _R); (2) fluorescence cross section of the admixture, and (3) Raman scattering cross section of water (nitrogen). The analysis showed that the fluorescent parameter (Phi) _O can be an independent characteristic of organic pollutants content in water (or atmosphere) parallel with the other optical indices of water quality (or atmosphere quality), for example, coefficients of absorption and of scattering, colorness index etc.

The inversion of lidar returns, i.e. the determination of the extinction or backscattering profile, is a classical example of an incorrect mathematical task. If one assumes single scattering approximation and known relation between both the extinction (alpha) (z) and backscattering (beta) (z) coefficients, then the remaining problem deals with the selection of the boundary value. Many authors agree that this is the key operation that determines the accuracy of the lidar data inversion. The utilization of the Klett's method requires estimating of the boundary value near the end of the sounding trace. Two common problems accompany this process. First is the very low value of the signal-to-noise ratio and the second is the lack of any kind of a priori information. In our previous work we investigated the proposed by us modification of the well-known slope method. It permits boundary value estimation if an isolated peak is present in the lidar return. Here we discuss the possibility of inverting the lidar return in the vicinity of an S-function extremum.