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Ahmadian N.,University of Greifswald | Hasan S.,Julich Research Center | Calla O.P.N.,International Center for Radio Science
International Journal of Microwave Science and Technology | Year: 2013

Studying the behavior of soil contaminated by diesel requires the measurement and calculation of electrical parameters such as permittivity and backscattering coefficient. It is also necessary to study the physical parameters such as surface roughness. The intent of this paper is to present a broad and updated overview of the diesel oil contaminated soil, emphasizing permittivity and scattering coefficient that are involved in determining and detecting the rate at which and extent to which hydrocarbons contaminate the soil and environment. The measurement of permittivity and the calculations of backscattering coefficient values were made with different amounts of diesel oil contamination and different incident angles in 5° intervals ranging from 10° to 80° for both horizontal and vertical polarization at C band. The values of scattering coefficient for different look angles (25°, 30°, 35°, 40°, 45°, 50°, and 55°) were calculated and are suitable for comparison with data generated from other remote sensing platforms. Accurate electrical parameter measurements of soil contamination and recognition of their dependence on physical and chemical composition are interesting and can support using microwave remote sensing instruments to observe the earth. © 2013 Nima Ahmadian et al. Source


Calla O.P.N.,International Center for Radio Science | Hasan S.,University of Pune | Ahmadian N.,University of Pune
Indian Journal of Radio and Space Physics | Year: 2011

In this paper, an attempt has been made to study the variability of dielectric constant of water contaminated by diesel at two different frequencies. The water samples with the salinity range of 5-50 kppm in an interval of 5 kppm have been measured. The weight percentage of diesel in water is from 0 to 280 percent with 20% interval in Cj band and 0 to 160 percent with 20% interval in Ku band. A simple, practical method of extracting the dielectric constant of water contaminated by diesel is presented in Cj band (5.3 GHz) and Ku band (13.4 GHz) with the help of waveguide cell with shift in minima method. It is concluded that the range of dielectric constant of water in combination with diesel in Cj band is wider as compared to Ku band. Moreover, the dielectric constant of water in combination with diesel is greater and differentiation of data was clearer in Cj band when compared to Ku band. Source


Calla O.P.N.,International Center for Radio Science | Rathore I.S.,International Center for Radio Science
Advances in Space Research | Year: 2012

Laboratory characterization of dielectric properties of terrestrial analogues of lunar soil (JSC-1A) and comparison with lunar samples returned from various Apollo missions is made at different as well as normalized bulk density. Here measurements of dielectric constants and losses were made at four microwave frequencies such as 1.7 GHz, 2.5 GHz, 6.6 GHz and 31.6 GHz. Complex permittivity of lunar simulant was measured at temperature ranging from -190 °C to + 200 °C using Wave-Guide cell method. Comparison of permittivity of JSC-1A with Apollo sample also has been done at similar microwave frequencies. The investigations reveal that dielectric constant and loss factor of terrestrial analogues of lunar soil are temperature dependent. As temperature is gradually increased both these parameter (storage factor and loss factor) also gradually increases. These temperatures were chosen because the Moon undergoes at that extremes level of temperature. It is scorching heat at 110 °C during the day and freezing cold at -180 °C during night. The measured value of can be useful for designing passive as well as active sensors. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved. Source


Calla O.P.N.,International Center for Radio Science | Ahmadian N.,University of Pune | Hasan S.,University of Pune
Indian Journal of Radio and Space Physics | Year: 2011

In case of low salinity or variable salinity, there is a very shallow radius of investigation. The dielectric constant of low saline water can be significantly modified by the presence of diesel. Techniques based on the propagation of electromagnetic waves may be used to detect contaminant and evaluate decontamination processes. Microwave remote sensing of diesel oil contaminated low saline water requires the study of electrical parameters of low saline water as well as diesel such as dielectric constant, emissivity and scattering coefficient along with their physical parameters like surface roughness, etc. The measurement of dielectric constant is very essential for estimating the emissivity and scattering coefficient. The measurement of dielectric constant of low saline water in combination with diesel has been carried out using waveguide cell with shift in minima method in 5.3 and 13.4 GHz. Tests are conducted with samples of different salinity of water with various amount of diesel oil. The amount of salinity is 5, 10 and 15 kppm and the amount of diesel contamination is from 40 to 280 percent with the interval of 80 percent for Cj band (5.3 GHz) and 40 to 160 percent with the interval of 40 percent for Ku band (13.4 GHz). The estimation of emissivity and scattering coefficient have been done for incident angles varying from 10 to 80 degree with the interval of 5 degree for both horizontal and vertical polarization. The value of Brewster angle has been calculated and the values of emissivity and scattering coefficient for three look angles (45, 50 and 55) degree is presented which are useful for designing space borne active and passive sensors. Furthermore, this database is useful for detecting oil spills in low saline water. Source


Calla O.P.N.,International Center for Radio Science | Bohra D.,International Center for Radio Science
Indian Journal of Radio and Space Physics | Year: 2014

The thrust of this study is to analyse the effect of scattering of electromagnetic waves on microwave links and tracking of low flying objects in the presence of strong ground bounce return from water bound areas. For this purpose, a ground based bi-static forward scatterometer has been used to generate co-polarized specular data at CJ, X, and Ku bands. The measurements are carried out on three types of water surfaces, i.e. tap water, natural lake water and saline water. All the three water surfaces are assumed to be slightly rough surfaces at the frequency of interest. Therefore, small perturbation model of slightly rough surface for forward scattering is a good selection to analyse data. The scattered microwave power from the terrain measured for 25°-70° scattering angle (θs) with an interval of 5° in specular direction with transmitting antenna placed at an incidence angle (θi) of 45° from nadir illuminates the terrain keeping øi = øs = 0° at 5.825, 9.472 and 13.4 GHz in CJ, X and KU bands, respectively for vv and hh polarization with different antenna heights. The forward scattering coefficient computed with the help of experimental geometry parameters, which then compared with estimated value of scattering coefficient obtained from small perturbation model of slightly rough surface. A good agreement between observed and estimated scattering coefficient for horizontal (hh) and vertical (vv) polarization has been found in X and KU bands with a polarization reversal in CJ band. It is also observed that dissolved salt or impurities increase the value of scattering coefficient. The basic purpose of this study is to map and monitor the natural resources and to provide timely inputs for the planners to develop appropriate strategies for optimum utilisation of the resources. Source

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