ALGORITHM FOR ESTIMATION OF ELECTROPHYSICAL PARAMETERS OF THE SURFACE BY ITS OWN MICROWAVE RADIATION

Reliable estimation of the electro physical parameters of surfaces using radiometric equipment is an actual area of remote environmental monitoring. The disadvantage of the procedures developed today for assessing the indicated properties of surfaces according to their own thermal radiation, prevents their practical use.In the framework of the statistical theory of detection-measurement based on the results of processing radiometric signals during multichannel reception, an identification method is developed and a decision-making rule were synthesized in favor of any of the hypotheses put forward about the values of the parameters of the observed surface.The methodology for solving the problem and the inherited identification rule meet the criterion of maximum likelihood. A distinctive feature of the synthesized decision-making rule: critical statistics based on the eigenvalues of the covariance observation matrix under multichannel reception conditions. The implementation uses standard computing operations.Moreover, a distribution density of critical statistics obtained because tabulated solving the problem. This circumstance makes it possible to set the required value of the significance level “apriori”, therefore, the value of the comparison threshold.Certification of the synthesized test is the rules for deciding in favor of the hypothesis about a given value of the components of the Fresnel reflection coefficient. It was carried out at the level of digital statistical modeling. The significance level was set equal to 0.05 and 0.1. Based on the simulation results, there were analyzed the dependence of the number of correct decisions (the fulfillment of the corresponding hypothesis) on the signal-to-noise power ratio for a given angular parameter of the signal.The performance characteristics obtained at the level of digital statistical modeling of the developed test confirmed, firstly, the conclusions of theoretical studies. Secondly, they give specialists in the field of development of radiometric systems the opportunity to evaluate both the effectiveness of synthesized tests at various numerical values of the probability of an error of the first kind and the complexity of their practical implementation.

An Efficient High-Frequency Method to Compute EM Scattering of a Target on Rough Surface

The physical optics and shooting and bouncing rays method are combined to rapidly compute the electromagnetic (EM) scattering from electrically large three- dimensional targets on a dielectric rough surface. To avoid modeling the rough surface of infinite extent, image theory is first used to account for the EM interactions between the target and the infinite planar surface. Next, the dielectric rough surface is accounted for by multiplying the Fresnel reflection coefficient with a roughness coefficient. In this way, only the target needs to be modeled. Thus, the proposed method can reduce significantly the computational costs and achieve a reasonable accuracy for the composite scattering problem, such as a ship-sea model.

Characterization and Application of a Grazing Angle Objective for Quantitative Infrared Reflection Microspectroscopy

A grazing angle objective on an infrared microspectrometer is studied for quantitative spectroscopy by considering the angular dependence of the incident intensity within the objective's angular aperture. The assumption that there is no angular dependence is tested by comparing the experimental reflectance of Si and KBr surfaces with the reflectance calculated by integrating the Fresnel reflection coefficient over the angular aperture under this assumption. Good agreement was found, indicating that the specular reflectance of surfaces can straightforwardly be quantitatively integrated over the angular aperture without considering nonuniform incident intensity. This quantitative approach is applied to the thickness determination of dipcoated Krytox on gold. The infrared optical constants of both materials are known, allowing the integration to be carried out. The thickness obtained is in fair agreement with the value determined by ellipsometry in the visible. Therefore, this paper illustrates a method for more quantitative use of a grazing angle objective for infrared reflectance microspectroscopy.

Evaluation and Analysis of Attenuated Total Reflectance FT-IR Spectra Using Kramers-Kronig Transforms

Two commonly used correction algorithms that were originally developed by Bertie and Dignam and their co-workers for quantitative analysis of ATR spectra are examined. It is shown that the Dignam theory is more suitable for strong ATR bands, whereas the Bertie algorithm is more applicable for weak bands. On the basis of analysis of possible deviation sources determined in the Bertie and Dignam theories, a new ATR algorithm is developed and analyzed. With this approach, the initial estimate of the absorption index spectrum is obtained by KK correlation of the intensity and the phase of the complex Fresnel reflection coefficient. An iterative process that minimizes the difference between the true and calculated reflectivity spectra while maintaining the KK relation between refractive and absorption indices is used in conjunction with the Maclaurin numerical KKT method. Such an approach appears to improve accuracies for both weak and strong ATR bands.