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Multi-frequency and multi-polarization measurements of changes of vegetated soil radar cross section and brightness temperature angular dependences

Keywords:

A. K. Arakelyan, A. A. Arakelyan, A. K. Hambaryan, M. L. Grigoryan, V. V. Karyan, G. G. Hovhannisyan


At present, radiophysical methods of sensing and corresponding microwave devices have wide application for solution of direct and inverse problems of the Earth surface and atmospheric remote sensing. For precise and unambiguous solution of bare and vegetated soils microwave remote sensing inverse problems it is necessary to improve radiative transfer models for soil and vegetation. For this purpose it is necessary and very significant to develop and to manufacture multi-frequency and multi-polarization complex of combined radar-radiometers at L-Ka-band of frequencies, suitable for short range remote sensing application and to perform field or quasi-field measurements under quasi-field and controlled conditions. In this paper data of spatio-temporally collocated, multi-frequency and multi-polarization microwave active-passive measurements of vegetated soil surface radar and radio thermal characteristics angular dependences are presented. The measurements were carried out for bare soil and for a soil covered by dry vegetation and by ash formed after arson of the vegetation cover. The results have been obtained during the measurements carried out in quasi-field conditions in the experimental site of ECOSERV Remote Observation Centre Co.Ltd. (ECOSERV ROC) built in Armenia under the framework of ISTC Projects A-872 and A-1524. The measurements were carried out at various polarizations by C (5,6 GHz), Ku (15 GHz) and Ka-band (~37 GHz) combined scatterometric-radiometric systems developed and built by ECOSERV ROC under the framework of the abovementioned Projects. Structural and operational features of the utilized system and the whole measuring complex are considered too. In the paper the curves of simultaneously mesured at 5,6 GHz, 15 Ghz and 37 GHz radar cross sections and brightness (antenna) temperatures angular dependences are presented, for dry and wet soil surfaces covered with dry grass (mixture of stems of dry wheat and herbaceous vegetation), for the soil covered with dry and cut grass, and for the soil covered with the ash after arson of dry grass. Data of measurements of dry soil surface (covered by dry cut grass) radar cross sections and brightness (antenna) temperatures at 30º incidence angle are presented too, for smock, fire, smolder and ash situations, measured respectively at «vv», «vh» (for scatterometers) and at «v» and «h» (for radiometers) polarizations. For comparison, data of measurements of clear air (sky) and lightly cloudy sky brightness temperatures at «v» and «h» polarizations are represented too, measured at 10º and 30º nadir angles of sensing.
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