In many areas of science and technology, there is a task to measure the optical and geometric characteristics of thin fi lms. The need to ensure the uniformity of measurements in this area led to the creation of the State primary standard of complex refractive index units GET 203-2012. In it, the complex refractive index was measured using spectral ellipsometry by measuring ellipsometric angles. However, this standard did not provide metrological support for coating thickness measurements when measuring their complex refractive index. In the period 2020–2023, VNIIOFI GET 203-2012 improved and expanded its functionality in terms of reproducing the unit of length in the fi eld of thickness measurements of optical coatings. The improved standard has been approved as the State primary special standard for units of complex refractive index and units of length in the fi eld of thickness measurements of optical coatings GET 203-2024. GET 203-2024 ensures the unity of measurements of complex refractive index and units of length in the fi eld of optical thickness measurements in the range from 1 nm to 50 μm. The range expansion was achieved by introducing an ellipsometer with an infrared range wavelength range equipped with an FTIR Fourier spectrometer. This range expansion is important for such industries as optics, microelectronics, optoelectronics, integrated optics and other areas of science and technology. This article presents the composition, operating principle and main metrological characteristics of GET 203-2024.

A technique has been developed for decomposing the values of two-dimensional spectral features according to their components of correlation coeffi cients. A close analogue of the proposed methodology are automatic classification algorithms. The basis of the methodology is the analysis of the proposed indicator – the products of normalized values of spectral features and their probability density. A nonparametric Rosenblatt-Parzen estimate is used to reconstruct the probability density from the initial statistical data. The peculiarity of the proposed indicator and the user-selected threshold values of the indicator make it possible to form variants of the decomposition of the initial statistical data and mapping of the results obtained during the computational experiment. Using a human-machine decomposition procedure for the values of two-dimensional spectral features, it is possible to circumvent the problem of solving optimization problems when using automatic classifi cation algorithms and use information about the relationship between spectral features in the elements of the earth’s surface. The results of the application of the technique in the processing of remote sensing data of the forest area and their comparison with the initial information are considered. Spectral features have been established, which mainly determine the decomposition between dead wood and other forest conditions. The obtained results reveal their development in the formation of sets of spectral features in the assessment of the states of natural objects.

An analysis of the destructive effect of external vibrations on radio-electronic equipment located on moving objects was carried out. The relevance of digital modeling of vibration impacts, aimed at long-term forecasting of the processes of origin and development of defects in on-board radio-electronic equipment, is substantiated. Vibration effects are considered from two points of view: on the one hand, as a factor in the destruction of equipment, on the other, as an informative signal indicating the nature and extent of this destruction. As equipment becomes more complex, the requirements for the adequacy of models and methods for assessing modeling errors increase. Digital modeling uses matrices constructed based on the equilibrium equations of elasticity theory. Based on these matrices, Lame coeffi cients are calculated and boundary conditions are formed. In the article, an explicit difference scheme is obtained, intended for the numerical solution of the system of equilibrium equations of the theory of elasticity. Factors infl uencing the modeling error have been identifi ed. The principles for calculating the vibration modeling error are formulated. Functionals are presented and justifi ed that connect the amplitude modeling error with the speed of vibration propagation in the medium under study and with the number of nodes of the discrete model for each projection of the vibration wave propagation vector. A specifi c numerical example shows how these functionals allow solving optimization problems.

The issues of correspondence of the results of direct and indirect measurements of optical density in a narrow wavelength band are considered. The optical density in a narrow wavelength band was measured by filtering the luminous flux according to the international standard ISO 5-3:2009 “Photography and graphic technology – Density measurements. Part 3: Spectral conditions” (direct measurement) and spectral method (indirect measurement). In order to ensure the uniformity of optical density measurements in a narrow wavelength band and establish the traceability of measurement results to the State Primary Standard of optical density units GET 206-2016, the degree of conformity of the results obtained by two methods was investigated. The techniques of measuring optical density in a narrow wavelength band for each method are described. The method of fi ltering the luminous flux was implemented using GET 206-2016, namely using a complex for measuring diffuse optical transmittance density. The Cary 7000 spectrophotometer (Agilent, USA) was used to implement the spectral method. Data on measuring the optical density of glass light fi lters by two methods are presented. A method for correcting the results of spectral measurements has been developed and a correction to the results of spectral measurements has been determined. The developed method and the correction make it possible to establish the correspondence of the results of spectral measurements to the results of measurements by fi ltering the luminous fl ux. Also, the described method for correcting the results of spectral measurements makes it possible to establish the traceability of the results of optical density measurements by the spectral method to the measurement results using GET 206-2016.

This paper considers the use of laser Doppler anemometry methods for non-contact measurement of the velocity of a moving medium in various phase states. It notes the specifi city of conditions of application of laser Doppler anemometers, in that in a number of cases there are restrictions on the use of photomultipliers. In order to find an alternative to the classic photomultiplier of a laser Doppler anemometer, three types of photomultipliers were investigated: classic electric vacuum; silicon avalanche multipixel; with microchannel plate. Physical experiments were conducted to measure the velocity of aero- and hydrodynamic fl ows by laser Doppler anemometer with photomultipliers of three types. The velocities of a rotating glass disk, aerodynamic fl ow in a channel of rectangular cross-section, and aerosol flow, as well as hydrodynamic flooded jet, were measured. The obtained experimental data were analyzed according to the criteria for assessing the quality (efficiency) of operation and finding the limits of applicability of the specified photomultipliers. Based on the physical properties of the studied photomultipliers, their efficiency indicators in various experiments are explained. The boundaries of the effective use of these photomultipliers in a wide class of physical experiments are determined. The results obtained are important for researchers involved in the study of aero- and hydrodynamic flows, where accurate and reliable measurements of flow velocity are required. The choice of an optimal photomultiplier tube for the laser anemometer allows increasing the accuracy and ease of obtaining experimental data and reducing the cost of the final equipment.

In this paper, the issues of calibration of the transmission coeffi cient of the antenna system of a ground station for monitoring the energy characteristics of signals from global navigation satellite systems are considered. The most commonly used method for calibrating the transmission coeffi cient of large-aperture mirror antenna systems based on solar radio emission is presented, its advantages and disadvantages are described. To eliminate the disadvantages of calibration based on solar radio emission (a limited range of working angles of the site, the need to involve thirdparty data on the spectral intensity of solar radio emission), an alternative approach to calibration based on an artifi cial source of radio emission placed on board an unmanned aerial vehicle is considered. The features of this approach are indicated – the need to work in the near zone of the measured antenna system, as well as the movement of an artifi cial radio source in a plane parallel to the plane of the aperture of the antenna system. A block diagram of the payload of an unmanned aerial vehicle for measurements in the near zone of the antenna system being measured has been developed. The results of a study of the characteristics of the payload signal generator of an unmanned aerial vehicle are carried out. A solution is proposed to eliminate the error in setting the output power of the signal generator (the difference between the nominal and actual signal power) from the measurement results. The necessity of using a control signal power meter and a bandpass fi lter as part of the payload is shown. A subsystem for monitoring the output power of the signal generator has been designed. Payload components have been selected that meet the limitation on weight and size characteristics. The possibility of remotely connecting the operator to the payload equipment of an unmanned aerial vehicle has been implemented. The perspective of the development of the payload layout is described.

The infl uence of diffraction effects at the edges of fl at samples of small (2–4 wavelengths of incident wave) sizes on the results of measurements of the refl ection coeffi cient of the sample material, a bistatic characteristic that depends on the frequency of radiation in a wide (10–85°) range of incidence angles is considered. To reduce the infl uence of diffraction effects, samples of various confi gurations have been developed, made of magnetodielectric with frequency dispersion of dielectric and magnetic permeability. The samples are a metal plate, on one side of which the material under study is applied, and the other surfaces of the plate are covered with radiation-absorbent material. The scattering characteristics of samples of the developed confi gurations are numerically calculated and experimentally measured on a bistatic facility in an anechoic chamber. The experimental results correspond with the calculated data. A noticeable reduction in the infl uence of diffraction effects on the refl ectivity values in a wide angular and frequency range has been shown. Using numerical methods in the FEKO software package, the infl uence of the sample confi guration on the methodical error in refl ectance measurements was studied. It is shown that this error can be reduced by using a substrate of an extended shape in the plane of incidence (samples of a hybrid confi guration). The results obtained can be used to measure the scattering characteristics of materials in free space.

The characteristic impedance of printed strip lines is determined by their design, cross-sectional geometry, relative permeability of the insulating base, and other factors that cannot be accurately estimated. The known methods for monitoring its frequency dependence using microwave measurements are not perfect and require further development. The proposed work proposes a method for experimental monitoring of the entire set of parameters of printed strip transmission lines: wave impedance, relative effective dielectric constant, as well as phase velocity and attenuation coeffi cient of a propagating electromagnetic wave. The characteristic impedance is determined by the s-parameters of the connection of coaxial strip junctions with a segment of an electrically long line. The wave parameters measured in the coaxial channel are transformed in the area of contact of the coaxial and strip lines, which makes it possible to obtain an analytical estimate of the wave impedance over the entire frequency range of the vector network analyzer or at least in its individual frequency windows. In the proposed method, the phase velocity, attenuation coeffi cient and relative effective dielectric constant are controlled by the differential-phase method based on the results of measuring the transmission coeffi cients of coaxial strip junction connections transformed to the contact areas by sections of electrically long and short printed stripline transmission lines. The performance of the proposed method for monitoring the parameters of printed strip lines is confi rmed by automated modeling, and its effectiveness is confi rmed by a full-scale experiment. The results obtained are useful to development engineers of integrated microwave technology and specialists in the field of monitoring object parameters in non-standard guide systems.

The results of work to expand the range of reference material of sorption properties are presented, namely, to create a reference material of the sorption properties of titanium dioxide, the use of materials based on which is widespread in many areas of industry. Two materials based on titanium dioxide were presented as candidates for CRM, and preliminary studies were carried out to establish the qualitative and quantitative composition, particle size, density, as well as parameters for preparing the material for research by gas adsorption. Based on the results, a material with a lower impurity content and particle size was selected. The metrological characteristics of the standard material were established using a reference installation from the State primary standard of units of specific gas adsorption, specifi csurface area, specific pore volume, pore size, open porosity and gas permeability coefficient GET 210-2019. The range of certified values of the specific surface area 10–100 m2/g, the range of values of the specific pore volume 0.05– 0.5 cm3/g, the range of values of the average pore diameter 2–30 nm and the range of values of specific nitrogen adsorption at liquid nitrogen temperature in the relative pressure range from 0.9·10–3 to 0.992 (0.01–20.00 mol/kg). The use of CRM 12390-2023 during calibrations, verifi cations, and tests in order to approve the type of instruments for measuring sorption properties at various stages of titanium dioxide production will improve the quality of products based on it.