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

Terrestrial snow cover has largest geographic extent in the northern hemisphere. Snow extent and snow depth are critical parameters in metro-hydrological models and are sensitive to the global climate change. The snow coverage and physical parameters play a special role in the global water and energy budget study. At present, radiophysical methods of sensing from the space and corresponding spaceborn and airborne microwave devices have wide application for solution of direct and inverse problems of the land snow cover-s remote sensing. Passive microwave satellite remote sensing can greatly enhance snow physical parameters measurements because of the ability to penetrate clouds, provide data during darkness and the potential to provide an index of snow depth and snow water equivalent. But one of the main problems in the application of satellite microwave radiometry for retrieval is the poor spatial resolution passive microwave remote sensing pixels. Each footprint of a satellite sensor may include several soil, vegetation and snow categories, which makes the measured brightness temperatures depend on the characteristics and fraction of each category. The high spatial variability of snow cover present a challenge for present methods of remote sensing of snow properties from space, particularly those based on passive microwave observations. Spatial detailed information on snow physical properties is required for several land surface and physical snow process modeling. Presently, no satellite system is in operation that provides this information with sufficient spatial detail and accuracy. Spaceborne high frequency (Ku- and X-band) active microwave sensors are considered as tools for sensing snow physical properties at a higher resolution to present passive instruments. For this reason a dual frequency (Ku- and X-band SAR mission CoReH2O, has been selected as a candidate Earth Explorer Core mission of ESA. However, for precise and unambiguous solution of snow microwave remote sensing inverse problem it is necessary to improve radiative transfer models for snow, 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 preliminary, spatio-temporally collocated, microwave active-passive and polarization measurements of soil snow cover-s radar and radio thermal characteristics angular dependences are presented. The measurements were 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 by C-band (~5.6 GHz), combined scatterometric-radiometric system ArtAr-5.6, developed and built by ECOSERV ROC under the framework of the above mentioned Projects. Structural and operational features of the utilized system and the whole measuring complex are considered too. The curves of soil snow covers radar cross sections and brightness (antenna) temperatures angular dependences simultaneously mesured at 5.6GHz for various snow depth and air temperature conditions are presented. The curves are built for various polarizations of radar («vv», «vh», «hh», and «hv») and radiometric («v» and «h») sensing.