A. N. Morozov

Substance recognition in the open atmosphere from a single Fourier transform spectroradiometer interferogram

An in-situ technique for identification of substances in the open atmosphere from the analysis of a single Fourier-transform spectroradiometer interferogram is described. A database of spectra of major atmospheric constituents and typical atmospheric paths is compiled to be used for the calculation of an atmospheric path with the following separation of a pollutant spectrum from the experimentally recorded spectrum. The identification of a substance by its spectrum is performed through sorting out substances from the database by the correlation coefficients and a quantitative analysis is performed by minimizing the discrepancy functional between the experimental and database spectra. The technique described is tested in situ.

Processing of double-sided interferograms subject to background self-radiation of an FTIR spectrometer

The effect of background (instrumental) self-radiation of a Fourier transform infrared (FTIR) spectrometer on the processing of double-sided interferograms is studied. From a theoretical analysis of the Michelson interferometer it was shown that when the brightness temperature of the object of study is close to the temperature of the instrument, the measured spectrum may contain inverted spectral ranges or isolated bands. The interferogram correction algorithms and experimental technique for elimination of the spectrum inversion and for compensation of the background self-radiation of the instrument are suggested.

Technique for obtaining and processing spectral information with static fourier spectrometer

We propose a technique and algorithm for processing interferograms obtained with a static Fourier spectrometer. Spectra of secondary radiation from certain compounds are obtained in the visible and near-UV spectral ranges upon excitation by different radiation sources. We present and discuss results of experimental data processing.

Sampling-free analysis of chemical compounds using a static Fourier-transform spectrometer

We have considered a technique for noncontact analysis of compounds and a device for its realization. To construct the device, we have proposed a static Fourier-transform spectrometer that is based on the phenomenon of interference in a wedge. A procedure for obtaining and processing emission spectra has been described. Interference patterns are recorded using sources of excitation radiation of 280 and 315 nm. Basic characteristics of the optical system have been calculated, and emission spectra of test objects have been presented.

Physical principles of the design of an interferometer with a rotating plate

This paper presents the design of an interferometer with a rotating plate for the wavelength range 8–12 μm. It is shown that the greatest difference of the optical path lengths in the interferometer arms is reached when the plate’s refractive index lies in the range 1.3–1.4. For a plate 10 mm thick, the maximum achievable spectral resolution is predicted to be 0.8  cm−1. The optimum range of angles of rotation of the plate is found for which the angular dependence of the optical path-length difference is linear. The technical appearance of an interferometer with no reference laser channel is discussed.

An imaging Fourier transform spectroradiometer with a multi-element photodetector for the spectral range of 7–14 μm

The construction and principle of operation of a imaging Fourier transform infrared spectroradiometer (FTIR spectrometer) equipped with a cooled 32-area photodetector designed for spectral analysis of open atmospheric paths are considered. The main technical characteristics of the Fourier spectrometer are reported. The technique of visualization of the detected vapor cloud is described. The results of field experiments using the imaging FTIR spectrometer are shown. Based on these results, the dynamics of motion of the cloud of material has been investigated, its angular and linear velocities have been estimated, and data on propagation of the cloud of material and change in its angular sizes in air have been obtained. A technique for analyzing data provided by two FTIR spectrometers is given, based on which one can estimate the size of the cloud and the distance to it from each device. It is shown that the results of detection of the cloud of material by the imaging FTIR spectrometer can be used to predict the propagation of material under study in space.

Portable Fourier spectroradiometer with an uncooled photodetector

This paper presents a portable Fourier spectroradiometer with resolution 8 cm−1, operating in the 7-14-µm range, with an MG-32 uncooled single-element pyroelectric photodetector. This Fourier spectroradiometer with uncooled photodetector is intended for remote determination of pollutant vapors in the open atmosphere, as well as for methane leaks on gas pipelines.

An algorithm for identification of substances using a finite set of secondary-emission spectra

A problem of identification of chemical composition in the absence of sampling procedures is considered. A method that allows identification using spectra of a desired substance is proposed. The measure of the difference between spectral sets is determined. The method is employed in the experiments using a visible and near-UV Fourier spectrometer. The secondary emission of samples is excited by UV sources with maximum intensities at wavelengths of 280 and 310 nm. Anthracene, POPOP, PPO, stilbene, and tryptophan are used in experiments. The ROC curves are constructed and compared to specify the parameters that are used in the algorithm for searching for substances in the database of reference spectra. The results will make it possible to improve the reliability and applicability of express analyzers of chemical substances.

Monitoring contaminants in the atmosphere by means of a Fourier spectroradiometer

An algorithm based on a model of constancy of temperatures on the path and in a cloud of contaminants is proposed for solving the problem of identifying and determining contaminant concentrations by means of a Fourier spectroradiometer. The main problems of the procedure for processing the initial interferograms and the experimental spectra are considered, including those with small radiance contrasts of the paths. The experimental results of field tests of a spectroradiometer based on the proposed algorithm are presented.

Passive location of chemical compounds using a Fourier-transform spectroradiometer

Fourier-transform spectroradiometers designed for searching, identifying, and determining the integral concentrations of vaporous chemical compounds in open atmosphere by the method of passive location are described. Characteristics and experimental data of field tests of the developed Fourier-transform spectroradiometers are presented.