International Center for Radio Science

Jodhpur, India

International Center for Radio Science

Jodhpur, India

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Ahmadian N.,University of Greifswald | Hasan S.,Jülich 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.


Calla O.P.N.,International Center for Radio Science | Singhal S.,International Center for Radio Science | Dadhich H.K.,International Center for Radio Science
Indian Journal of Geo-Marine Sciences | Year: 2015

For detection of the cyclone PHET, brightness temperature data (BT) of Special Sensor Microwave/Imager (SSM/I) sensor at 19.35GHz over Arabian Sea (AS) was procured for the year 2010. In order to trace the cyclone PHET; study of the cyclone affected area before and after striking of the cyclone affected day is done. During analysis at 19.35GHz, the BT and rain rate data over cyclonic area was found to be exceptionally high when compared with the ordinary days. This behavior could be due to the presence of rain clouds during cyclone that emit more radiation at lower frequency (< 37GHz) than the background ocean and cloud free atmosphere. Surface roughness that is caused by high winds increases the BT. As a result at 19.35GHz the BT is found to be high at cyclonic areas as this frequency is greatly affected by rains and high winds. This result shows an insight to detect the natural hazards using passive microwave remote sensing. © 2015, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.


Calla O.P.N.,International Center for Radio Science | Mathur S.,International Center for Radio Science | Jangid M.,International Center for Radio Science | Gadri K.L.,International Center for Radio Science
Earth, Moon and Planets | Year: 2015

The paper presents a case study of inconsistent behaviour of Chandrayaan-1 Mini-SAR and LRO Mini-RF data over south polar lunar craters. The paper includes analysis of Stokes parameters and characterization of received time-varying electromagnetic fields over the south pole lunar craters. For the study, Chandrayaan-1 Mini-SAR and LRO Mini-RF data at 2.38 GHz are used. Total five lunar craters in south polar region are analyzed to study the effect of various parameters on the polarization of the signal. We have compared linear horizontal (LH) and linear vertical (LV) polarization components of received radar signal over the same targets using two different SAR data. Ratios of received LH to LV components are also derived over the five craters. It is observed that Chandrayaan-1 Mini-SAR is receiving high LH component as compared to LV component. This is not consistent with the scattering theory (Fawwaz et al. in Microwave remote sensing active and passive, Artech House Inc., New York, 1981), which states that for incidence angle greater than 15°, the vertical polarized component of a received signal should be always high as compared to horizontal polarized component over rough surfaces. These inconsistent results of Chandrayaan-1 Mini-SAR are observed over all five craters. In the paper, various effects of sensor parameters like incident angle, ellipticity angle, orientation angle etc. on scattering mechanism are discussed to understand the inconsistent behaviour of two SAR data over same target. © 2015, Springer Science+Business Media Dordrecht.


Calla O.P.N.,International Center for Radio Science | Dadhich H.K.,International Center for Radio Science | Singhal S.,International Center for Radio Science
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2013

At global level, detection and mapping of oil spill distributions is not feasible manually, as it is a time consuming process. Therefore, this task can be accomplished only by using satellite microwave remote sensing techniques. Due to the unique all weather penetration capability of microwaves it can penetrate through clouds and provide data during day as well as at night. The microwave remote sensing will provide the opportunity to measure the extent of oil spills over the sea surface and the thickness of oil over the sea surface. The paper describes briefly the specification of Special Sensor Microwave Imager (SSM/I) and Advanced Microwave Scanning Radiometer for EOS (AMSR-E) satellite and present a relationship between brightness temperature at different frequency with different oil spill and non-oil spill locations. The detection of oil spill has been done over a large frequency range from 6 GHz to 91 GHz and the behaviour of brightness temperature over oil spill location as well as non- oil spill location for each frequency is analyzed. The oil spill detection technique using the multifrequency brightness temperature has been revealed in this paper. The study is based on the 2010 Mumbai oil spill, which occurred after the two Panamian-flagged ships, MSC Chitra and MV Khalijia-III collided off the west coast of India. © 2013 IEEE.


Calla O.P.N.,International Center for Radio Science | Mathur S.,International Center for Radio Science | Jangid M.,International Center for Radio Science
Journal of Earth System Science | Year: 2014

The Lunar Reconnaissance Orbiter (LRO) has a miniature radio-frequency (Mini-RF) payload, i.e., the Synthetic Aperture Radar (SAR) that has provided very fundamental information about the lunar surface and subsurface which was not known inspite of many manned and unmanned missions. Microwave sensors are used for analyzing the equatorial region of the Moon (60°N to 60°S) which is covered with many well-known craters like Kopff, Taylor, Maunder, Descartes, Jackson and Santos Dumont, each having different topography. The LRO data in terms of the scattering coefficient (σ ° LH and σ° LV) with incidence angle of 49° has been used for computing physical and electrical parameter of lunar surface and to learn more about the impact cratering process. Most of the lunar surface shows small Circular Polarization Ratio (CPR), i.e., the reversal of polarization is normal, but some targets have high CPR. In this paper we have discussed the scattering behaviour of lunar equatorial region where the value of CPR >1. Studies say that the LV intensity is always greater than LH but from the data obtained from LRO, it is observed that it varies at each pixel depending upon the target properties under radar view. © Indian Academy of Sciences.


Calla O.P.N.,International Center for Radio Science | Dadhich H.K.,International Center for Radio Science | Singhal S.,International Center for Radio Science
Indian Journal of Radio and Space Physics | Year: 2013

Oil spill pollution is a severe environmental problem, which persists in marine environment or in inland water across the world. It has grown to an alarming magnitude with increased levels of oil production and transport. Thus, it is important to study and analyze this environmental pollution. The study and detection of oil spills can only be accomplished by satellite microwave remote sensing techniques. As microwaves have unique all weather penetration capability and can be used both in day and night, it does not require illumination of target from the sun. Two types of microwave sensors [Ulaby F T et al. Microwave remote sensing - Active and passive, Vol 1 and 3, 1981] exist: one is passive sensor and other active sensor. Passive microwave sensor is radiometer that operates in the microwave region and detects microwave radiation emitted by the earth surface in addition to passively sensing emissions coming from objects on Earth. Active microwave sensor emits microwaves toward the earth's surface. These microwaves are reflected back from earth's surface and return back to the sensor. In this paper, for the detection of oil spills, data of passive microwave sensors onboard Special Sensor Microwave/Imager (SSM/I) [Hollinger J et al. Special Sensor Microwave/Imager user's guide, 1987, 120] satellite at 19.3 GHz frequency is used and analyzed. The analyses shows sudden decrease of brightness temperature values in both horizontal and vertical polarization over the oil spill area (Bombay High Area, Arabian Sea) when compared to the brightness temperature values over oil free area in the Arabian sea.


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.


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.


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.


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.

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