Estimation and analysis of the parameters of a field spectroradiometer covering the spectral range 350–2500 nm

Abstract

We describe selection of an optical layout for a spectroradiometer for rapid field diagnostics of the status of agricultural and forest vegetation, soils, and other objects over a broad spectral range (350-2500 nm), and we present calculations of the basic operating parameters of the spectroradiometer. The spectroradiometer makes it possible to make measurements of the absolute values of the spectral radiance and the relative characteristics of reflected radiation for both individual components of plants as well as for plants as a whole and plant communities.Introduction. Reflectance spectra of natural objects, obtained with remote measurements in the visible and near IR ranges, are highly informative and have been successfully used to assess the status of the objects. Considerable differences between the reflection coefficients of objects in different ranges of the electromagnetic spectrum, depending on the type and status of the objects and the illumination conditions, are why it is possible to use remote (contactless) spectral methods to determine the characteristics of vegetation and soil objects [1,2]. At the moment, there is good reason for needing to use increasingly narrow spectral channels, with the possibility of choosing them in a targeted way in determining different biophysical parameters of plants [3][4][5][6]. Furthermore, we need to expand the working spectral range up to 2.5 μm, since in the interval 0.9-2.5 μm we find absorption bands for water and plant proteins included within cells of leaf tissue and determining the spectrum of radiation leaving the leaf, carrying information about the composition of the cell, the genotype, the properties and status of the plant as a whole. Important information about the structure of leaf tissue is also provided by the degree of polarization of the reflected radiation.A potentially important area of application of high spectral resolution data in the range 0.35-2.50 μm is plant selection. One way to obtain information about the genotype is to study the optical polymorphism of the cell structures, in particular proteins, which can be considered markers for the corresponding genes. Using high-resolution spectrometers in the 0.35-2.50 μm range, taking into account the state of polarization, will allow us to determine the marker parameters in the spectral "portrait" of the genotype and to significantly speed up the process of practical plant selection. All the measurements in this case should be done under field conditions in vivo.Another problem in agricultural production which can be solved using a high-resolution field spectroradiometer in the 0.35-2.50 μm range is determination of the quantitative mineral composition and moisture content of the soil, since the most important absorption bands needed for soil analysis lie in the range 2.0-2.5 μm.In order to solve these and other problems, we need to design a relatively inexpensive spectroradiometer for one-step recording of the full spectrum in a broad spectral range, with high spectral resolution and the poss...

Methodology for Regional Soil Organic Matter Prediction with Spectroscopy: Optimal Sample Grouping, Input Variables, and Prediction Model

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