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Synthetic Aperture Radar (APSAR), 2011 3rd International Asia-Pacific Conference on

Date 26-30 Sept. 2011

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Displaying Results 1 - 25 of 268
  • KOMPSAT-5 calibration and validation processor

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (485 KB) |  | HTML iconHTML  

    In order to make the best use of the data produced by the KOMPSAT-5 (K5) Synthetic Aperture Radar (SAR), there is the need to perform a continuous process of calibration during the operational lifetime of the system, based on data acquired over targets of known characteristics with supporting data provided by the instrument itself. The main aim of the Radiometric Calibration process is to relate the pixel intensity in the imagery output by the SAR processor to the radar cross-section on the ground. View full abstract»

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  • KOMPSAT-5 SAR P/L on ground verification campaign

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    In the frame of KOMPSAT-5 program, the Korean Aerospace Research Institute (KARI) mission to collect SAR images relevant to Korean Peninsula, Thales Alenia Space Italia (TASI) developed the SAR Payload System. The KOMPSAT-5 Payload is composed by a SAR Sensor Subsystem (SSS) including all the radar functions and a Data Link Subsystem (DLS) to store data onboard and transmit them on ground. Before of the Payload integration process, all the components have been subjected to appropriate acceptance test campaigns and, afterwards, the SSS and DLS have been verified separately to collect all the measurement data needed to compute the key performance parameters. The complete functionality of Payload has been verified after the installation of SSS and DLS on the structure of the Payload Module (PLM). Finally, following the delivery of the SAR Payload to KARI facilities, the PLM has been assembled with the Service Module, and the overall verification campaign of the Satellite has been completed in South Korea. Aim of this paper is to presents the SAR Subsystem on ground verification approach outlining the different phases of the verification process, the main objective and the results. View full abstract»

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  • KOMPSAT-5 SAR design and performance

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    KOMPSAT-5 is an Earth Observation mission funded by the Korea Aerospace Research Institute (KARI) in order to collect SAR images of the Korean Peninsula for the Korean Geographic Information Systems and for the Korean environment and disaster monitoring System. This paper presents design and performance of the X-band Synthetic Aperture Radar developed by Thales Alenia Space Italia in the frame of this program. View full abstract»

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  • Orbit maintenance for calibration of KOMPSAT-5

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    The first Korean SAR mission satellite, KOMPSAT-5 will be launched atop of Russian Dnepr rocket. The satellite is injected into Sun-synchronous dawn-dusk orbit at the mean altitude of 550 km. The satellite orbit has a characteristic of exact repeat ground track for 28 days. There are total 421 reference longitude points around the Earth equator to maintain the ground path of the satellite within ± 2 km longitude band. The ground track maintenance requirement is specified for obtaining interferometry radar image from KOMPSAT-5. After releasing from the launch vehicle, the satellite should acquire a nominal ground track within 2 months for SAR calibration and validation. In order to calibrate the SAR payload, total of 52 corner reflectors are constructed in Mongolia. The satellite should pass over the corner reflectors with three imaging mode and two looking mode during 4 months of calibration and validation period. The satellite orbit should be carefully maintained to follow the exact repeat ground track at that time. In this paper, the acquisition and maintenance of the KOMPSAT-5 satellite reference ground track will be presented. The ground track acquisition after separation from Dnepr launch vehicle is analyzed using simulated spacecraft orbit data. A series of orbit maintenance maneuvers to keep the satellite following the reference ground track are presented. View full abstract»

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  • RCS measuremet and analysis of corner reflector and its background for KOMPSAT-5 calibration and validation

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    Radiometric Accuracy of SAR Image is one of the most important requirements for KOMPSAT (Korea Multi-Purpose SATellite)-5 and it is the main objective of calibration and validation procedure. The radiometric calibration can be divided into relative and absolute radiometric calibration. Point targets whose RCS (Radar Cross Section) can be evaluated with the close-form equation are required to perform absolute radiometric calibration. CR (Corner Reflector) is the most well-known reference ground target, because it has significantly large RCS compared to backscattering coefficient of background and it is easy to evaluate the RCS from its geometrical shape. In addition, background level of CR is also important factor for absolute radiometric calibration, because high signal-to-clutter ratio is determined from not only high RCS level of a point target but also low background level. The measured RCS of the CR and analysis background level of Mongolian site are shown in the paper, in order to represent that RCS of the CR is very accurate and background level of Mongolian site is significantly low for the KOMPSAT-5 calibration. View full abstract»

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  • Simulation of complex target RCS with application to SAR image recognition

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    SAR(synthetic aperture radar) image understanding and interpretation is essential for remote sensing of earth environment and target detection. In development of aided target recognition and identification system, SAR image database with rich information content plays important role is essential. This paper presents a RCS computation for simulation of orbital SAR image. After demodulation, the received SAR signal is given as [1-2] s0(τ, η) = A0 wr(τ - (2R(η))/c, Tp)wa(η) exp{- j (4πfcR(η))/c + jπαr(τ - (2R(η))/c)2 + φ"} (1) where φ" is lumped sum of phase noise from atmosphere, satellite altitude error, terrain, etc. and R is distance from antenna to target being observed, A0 is slant range backscatter coefficient of the target, φ the phase term, and wa(η) is antenna pattern and is a function of slow time. To take into account the radar backscattering characteristics in (5), we apply Radar Cross Section Analysis and Visualization System (RAVIS) [3] that utilizes the physical optics (PO), physical diffraction theory (PDT), and shooting and bouncing rays (SBR) to compute the RCS of complex radar targets [4-8]. Single scattering and diffraction from a target are first computed by PO and PDT, followed by SBR to account for multiple scattering and diffraction. The system outputs for a given 3D CAD model of the target of interest. The CAD model contains numerous grids or polygons, each associated with computed RCS as function of incident and aspect angles for a given set of radar parameters. The number of polygons is determined by target's geometry complexity and its electromagnetic size. To realize the imaging scenario, each polygon must be properly oriented and positioned based on proper coordinates system. SAR image is sensitive to target's - - geometry including orientation and aspects angles. For target recognition and identification, more complete database for feature extraction is preferable to achieve better performance and reduce false alarm rate. In SAR image simulation, supposed N samples (incident angles and aspect angles) is desired, then the computation complexity is O(N3). Statistics indicate that with 1.97 GB RAM and 2.4GHz (4 cores) CPU to complete one TerraSAR-X image simulation of MD80 aircraft using 25672 polygons representing RCS for a pose (one incident angle and one aspect angle) it would take about 11 months to complete all poses for incident angle from 20° -50° with 5° a step and aspect angles from -180° ~+180° with 1° a step (total 2520 poses). View full abstract»

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  • Characteristics of time-reversal(TR) SAR image of point target

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    In this paper, we investigate the time-reversal SAR image of a point target buried in a cluttered environment. To mitigate the complexity of the problem, we use a simple scattering model that consists of randomly distributed point scatterers as a cluttered environment. The RDA(Range Doppler Algorithm) is adopted as an image processing algorithm. View full abstract»

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  • Development of a scattering model for bean fields from scatterometer system and X-band SAR

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (806 KB) |  | HTML iconHTML  

    This paper presents a scattering model and measurements of backscattering coefficients for bean fields. The polarimetric radar backscatters of a bean field were measured using the ground-based X-band polarimetric scatterometer in an angular range from 20° to 60° in 2009 and 2010. The backscattering coefficients were also obtained using the COSMO-SkyMed (Spotlight mode, HH-mode) from July to October 2010. The backscattering coefficients of the bean field were computed using the first-order radiative transfer model (RTM) with field-measured input parameters. The bean layer is composed of the stems, branches, leaves, and the beans. Therefore, the stems, branches, and beans are counted as the cylinders, the leaves are accounted for by the leaves. It was found that the estimated backscattering coefficients agree quite well with the field-measured radar backscattering coefficients. View full abstract»

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  • Some extensions to the integral equation method for electromagnetic scattering from rough surfaces

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    The traditional models for wave scattering from random rough surfaces are the small perturbation method (SPM) and the Kirchhoff model (KM), which are applicable for slightly rough surfaces and surfaces with small surface curvatures, respectively [1]-[3]. In order to bridge the gap between SPM and KM, several so-called unifying methods have been developed, including the small slope approximation (SSA) [4], the phase perturbation technique (PPT) [5], the operator expansion method (OEM) [6], the unified perturbation method (UPM) [7], [8], the full wave approach (FWA)[9], [10], and the integral equation method (IEM)[11]. The ability to provide good predictions for forward and backward scattering coefficients has made IEM one of the most widely used analytical models. Yet to make the derivation of this model mathematically tractable, several assumptions were made, including [12]: 1) the removal of the spatial dependence of the local angle of incidence of the Fresnel reflection coefficient by either replacing it with the angle of incidence or the specular angle; 2) For the cross polarization, the reflection coefficient used to compute the Kirchhoff fields is approximated by 0.5(R|| - R); 3) Edge diffraction terms are excluded; and 4) Complementary field coefficients are approximated by simplifying the surface Green's function and its gradient in the phase terms. Concerns over the assumptions have prompted several modifications and variations of IEM in the literature. This paper represents a brief recapitulation of our work on Assumptions (1) and (4), respectively. Assumption (1) is an oversimplification of the statistical behavior of the unit normal n directed out of the surface at an arbitrary point on the surface. Specifically, n is effectively restricted to a deterministic quantity, with the direction depending on the angles of incidence and scattering, while giving up all its statistical features, which stem from the fact that the unit - - normal follows a statistical distribution, and moreover, unit normals corresponding to different points on the surface are correlated. It is such correlation that presents technical challenge if a sound compromise between model fidelity and complexity is to be made. In this regard, we proposed a statistical model for electromagnetic scattering from a Gaussian rough surface in conjunction with the IEM formulism [13], where the statistical features of the surface slopes and the effect of shadowing are included. In evaluating the Kirchhoff incoherent power, for the correlated term due to correlation between the normal vectors of two neighboring points on the surface, an approximation scheme based on the decomposition of the covariance matrix is proposed. For the cross and complementary incoherent powers, due to their subdominant nature, the cross correlations between the surface slopes at different points on the surface are neglected to reduce the computational complexity. In dealing with Assumption (4), regarding the spectral representation of the Green's function, the simplification was discarded and full form was restored, resulting in a modification to the complementary components. The resulting model is the so called improved IEM model (I-IEM)[14]. Additional restoration of the spectral representation of the gradient of the Green's function in its full form leads to the advanced IEM model (AIEM)[12] and the IEM2M model[15]. However, there are some technical subtleties in connection with the restoration of the full Green's function that have not been adequately reflected in these models. For example, in evaluating the average scattered complementary field over height deviation z, a split of the domain of integration into two semi-infinite ones is required due to the absolute phase term present in the spectral representation of the Green's function. We demonstrated that this operation will lead to an expression containing the error function. Inclusion of the e View full abstract»

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  • Electromagnetic scattering from a corn canopy at L and C bands

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    The ability to retrieve and monitor soil moisture and vegetation water content (VWC) is of great importance. Yet accurate retrieval of such information from microwave observations presents a big challenge, which calls for the development of high fidelity scattering models. In the literature, a ”discrete scatter” approach was usually deployed, which attempted to determine first the scattering behavior of the individual constituent of the canopy, then that of canopy as a whole by summing up either incoherently [1] [?] or coherently [2]-[3]. To simplify the problem, constituents of the canopy are modeled as canonical geometrical objects. For corn canopy, the stalks are modeled as dielectric circular cylinders with finite length, and the leaves are represented as thin dielectric disks with elliptic cross section. Since scattering from each of the canonical object serves as the base for further ”assembling”, it is expected to be accurately determined. However, mush is still desired in this regard. For a dielectric cylinder of finite length, in studying its scattering behavior the generalized Rayleigh-Gans approximation (GRGA) [4] is usually applied, which approximates the induced current in a finite cylinder by assuming infinite length. This method is valid for a needle shaped scatterer with radius much smaller than the wavelength. Yet caution must be taken even at L band when EM scattering from the stalk of a corn plant is to be evaluated using GRGA. It is also well known that GRGA fails to satisfy the reciprocity theorem [2]. In the evaluation of scattering amplitude of leaves, the GRGA method is usually used. However, caution must be taken here. At C band the wavelength is 5.6 cm, which is comparable to the length of minor axis of corn leaves, which presents an unfavorable condition in applying GRGA and thus appreciable error is expected in the predicted scattering amplitude. When corn canopy is at its early stage of growth, or when the- - incidence angle is not large, contribution from the underlying ground is appreciable and thus its accurate prediction is important. Yet this roughness effect has not been adequately addressed in canopy scattering models, where what is typically applied is conventional analytical method such as Kirchhoff approximation (KA), or the small perturbation method (SPM) [5], or the more advanced yet still improvement-needed integral equation method (IEM) [6]. In this study, we choose to apply a more rigorous treatment of the rough surface contribution using the recently advanced EAIEM model by the authors [7]. With the advancement of several scattering models of dielectric cylinder and disks and of rough surfaces, it is the aim of this paper to investigate if a coherent combination of these constituent models can improve predictive power of the resultant canopy scattering model. To be more specific, in analyzing electromagnetic scattering from a dielectric cylinder of finite length, we use the new approach that we have recently proposed [8], where a long cylinder is divided into a cluster of N identical sub-cylinder by using N - 1 hypothetic surfaces, for each the T matrix can be calculated stably in the numerical sense. The boundary conditions at the hypothetic interface are treated carefully. A system of equations is set up for each sub-cylinder, and the overall system of equations is coupled and linear, thus can be solved by appropriate iterative method. Moreover, the VPM method is found to be applicable to dielectric cylinders of arbitrary length as long as the T matrix is attainable for the elementary sub-cylinder. The applicable relative dielectric constant can go up to 70 (real part), which is normally the upper bound for corn stalks at C band. The radius of the cylinder can be as high as 5 wavelengths, a feature of the model that is expected to be useful for forest applications [9]. Scattering from rough surface is treated using the EAIEM model [7], which is a uni View full abstract»

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  • A fast normalized cross-correlation algorithm for InSAR image subpixel registration

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    A fast normalized cross-correlation algorithm (Fast-NCCA) is proposed for InSAR image subpixel registration considering the interferometric cases of gentle topography and/or short baseline. The conventional normalized cross-correlation algorithm (NCCA) searches for the optimal subpixel offset by oversampling either the coarse cross-correlation or the InSAR image pair. The offset estimation accuracy is restricted by the oversampling rate and the computational burden is heavy when high accuracy is demanded. In this paper, the oversampling and correlation searching process of NCCA is transformed into a nonlinear optimization problem which takes the coherent cross-correlation as the objective function, and by solving it with the sequential quadratic programming algorithm, the subpixel offset between the images can be fast and accurately obtained. Experiment on SIR-C/X-SAR data shows that the proposed algorithm performs very well not only on the speed but also on the accuracy. View full abstract»

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  • Classification of forest vegetation species based on parameters of tomography

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    In this paper, we propose a method to extract multi-parameters regarding to tomography from PolInSAR data and investigate the potential of applying them to classify the forest vegetation species. We first propose a general volume scattering model that includes three basic scattering profile structures according to the change of extinction. Then three basic geometries of trees are introduced and their corresponding scattering profiles in HH-VV and HV channels are developed by the combination of three presumptive profiles. Supposing the contribution values of the three geometries to the final complex coherence is a, β and γ respectively, the total vertical structure of a general tree can be reconstructed. By resolving the equations between coherence and each contribution component the three contribution values can be calculated and then are used to identify the tree species. Finally this method is validated using simulated data. View full abstract»

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  • Indoor experiment on vegetation permittivity measurement using Brewster's angle

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    Vegetation monitoring is one of the major applications of polarimetric synthetic aperture radar (PolSAR). In this paper, permittivity estimation method for vegetation by using multi-angle polarimetric radar is proposed. The method utilizes Brewster's angle of double-bounce scattering component. We demonstrate validity of the proposed method by indoor model experiments. We use a dihedral reflector and dipole cloud to obtain double-bounce scattering and volume scattering, respectively. The experimental results show that the proposed method works properly when volume scatterer exists. View full abstract»

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  • X-band T/R module based on GaN MMICs power amplifier

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    In this paper a novel X-band T/R module based on a GaN-HEMT MMICs high power amplifier chain, comprising a driver amplifier (DA) and a high power amplifier (HPA) will be presented. A multifunction chip is integrated in the T/R module to reduce the size and weight. The DC control electronics is designed based on multi-layer low temperature co-fired ceramic (LTCC) technology. Output power level of 43 dBm (20 W) for the T/R module is measured. View full abstract»

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  • Design of X-band receiver on airborne SAR/GMTI multi-model reconnaissance radar

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (386 KB) |  | HTML iconHTML  

    Research of synthetic aperture radar (SAR) for Moving target detection and imaging has huge value of military and civilian, a great many of countries are seeking to study motion detection and imaging technology, and to seek efficient and practical method and new system, especially to study the ground of moving target detection and imaging (SAR / GMTI) technology, With the development of airborne SAR radar system, its requirements not only the system size, weight and reliability continue to increase, but also dynamic and the radial resolution of the ground targets, This paper discusses the experiment situation of a receiving channel X-band of airborne SAR / GMTI multimode battlefield surveillance radar, the receiver channel adopt the technology of MMIC circuits micro-assembly and circuit embedded, it make breakthrough at the key technologies of multi-channel consistency and multi-mode, integration and miniaturization. View full abstract»

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  • Ice sheet motion in inland Antarctica from ALOS PALSAR interferometry

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    To detect the surface displacement fields and their seasonal change of ice sheets in Antarctica, ALOS PALSAR interferograms over the Yamato mountains area investigated. One of two paths overlapping each other shows a substantial change from winter to summer. Detailed analysis suggests that the change is caused by not the seasonal effects but ionospheric effects by aurora activities. View full abstract»

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  • Identification of rice fields in a complex land-use region using RADARSAT-2 data

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    In the studied watershed, the land-use is complex, the cloud cover is frequent, and the medium resolution of optical images (LANDSAT, SPOT) make rice detection a challenge. To solve these problems, polarimetric radar data was used from RADARSAT-2 (C-Band). This paper addresses a classification scheme to extract rice fields based on the analysis of the temporal variation of backscattering coefficients in horizontally (HH) and cross-polarized (HV) polarization and the Support Vector Machine (SVM) classification algorithm. The results confirm that HH is better than HV polarization for rice detection because the rice backscattering coefficient in HV is not significantly different from the coefficients from other vegetation types. Preliminary results also show the capabilities of RADARSAT-2 C-band polarimetric images to identify rice fields. View full abstract»

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  • A resynthesis framework for PolSAR images based on feature selection

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    Compared with optical remote sensing images, PolSAR images is hard to be interpreted by human eyes. In order to improve the visual interpretability and automatic interpretation, an effective resynthesis framework is developed in this paper to highlight the interesting targets for PolSAR images. The resynthesized images are constructed by the method similar with polarization synthesis which inputs different combinations of polarization parameters extracted from original PolSAR images into three channels of a display space. Since almost complete polarization information extracted from PolSAR images has been used in our framework, feature selection method is needed to choose the most essential parameters for resynthesizing. Experimental results demonstrate that our resynthesized PolSAR images are more readable and more intelligible. View full abstract»

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  • Change detection in urban areas of high-resolution polarization SAR images using heterogeneous clutter models

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (303 KB) |  | HTML iconHTML  

    Based on the clutter statistical characteristics of fully polarimetric SAR image, this paper presents a novel method for SAR change detection based on the heterogeneous clutter model. We use spherically invariant random vectors (SIRV) distribution model to fit the urban areas of full polarimetric images. Then, the degree of evolution between the statistical characteristics of multi temporal full SAR images is measured by the polarimetric likelihood ratio test (PLRT) model. Afterwards, Minimum error method (KI) threshold segmentation is applied to extract the `real' changed area for change detection. Two RadarSat-2 fully polarimetric images for Suzhou city in China, acquired on April 9, 2009 and June 15, 2010 separately, are used for our experiment. Compared with the detection results based the Wishart distribution model, it is shown that the heterogeneous clutter not only fits urban areas better, but also can avoid large number of false alarms. View full abstract»

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  • Detection of ship targets near coastline by using Doppler Beam Sharpening technique

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    If ship targets are near the coastline or islands, it's very difficult for the conventional anti-ship missile to detect them because the echo signal from the land inside the beam-width and same range resolution with the target can hide the target. As the missile approaches the target, the area and RCS of the land patch gets smaller, so that the conventional anti-ship missile can only detect the target at the very short range. The DBS(Doppler Beam Sharpening) technique is known to have been applied to the anti-ship missile to detect the ship target at the long range by discriminating the target from the land by using the difference of Doppler frequency. In this paper we investigate the principle of DBS technique theoretically and analyze the effectiveness by computer simulation. View full abstract»

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  • Limits of target tracking in heavy clutter

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    The Integrated Track Splitting (ITS) filter is an advanced method for automatic target tracking in clutter. The track trajectory state probability density function (pdf) is approximated by a mixture of track component pdfs. The track state includes a track quality measure (the probability of target texistence) which is used to discriminate between true and false tracks. This paper investigates the feasible limits of target tracking (False Track Discrimination) in heavy clutter and low probability of detection. Relationship between the False Track Discrimination performance and the component control parameters is part of the investigation, thus some practical guidelines for ITS filter design are also provided. The tradeoffs between performance and computational resources are indicated, allowing for the proper design of ITS filter and hardware resourcing. View full abstract»

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  • Target detection and angle estimation using 3 channel ΣΔ STAP

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    ΣΔ STAP which uses sum and difference beams of an antenna has significant practical advantages in clutter suppression. On the other hand, when we use ΣΔ STAP for target detection, we use mono-pulse strategy to estimate off-axis target angle. However, signals used for target estimation are contaminated by clutter and induce erroneous result. The conventional ΣΔ STAP is modified to estimate target angle accurately and to improve target detectability, simultaneously. View full abstract»

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  • Control about sea clutter level of marine RADAR

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    In this paper we reduce the sea clutter level of marine RADAR systems using improvement factors and velocity spreads. The sea clutter consists of sea state and wave height. The proposed method controls effectively the sea clutter in 1~7 levels. The sea and rain clutter velocity spreads also vary depending on the clutter size. The improvement factor of clutter is also predefined by calculating the clutter level. Pre-defined clutter level can be reduced sea and rain clutter from RF receivers. View full abstract»

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  • SAR and optical data utilization for soil moisture retrieval in vegetated region

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2312 KB) |  | HTML iconHTML  

    This paper presents a fusion of information approach to retrieve the soil moisture in vegetated area with requirement of minimum apriori information. A normalization approach of scattering coefficient of vegetated area has been utilized so that normalized scattering coefficient becomes a function of vegetation only. The vegetation can also be modeled with NDVI, a vegetation index. An empirical relationship has been developed between normalized scattering coefficient and NDVI. This empirical relationship provides the scattering coefficient of bare soil which is inverted with Dubois model to retrieve volumetric soil moisture content. View full abstract»

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  • Development of active transponder for KOMPSAT-5 mission

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    KOMPSAT-5 has a benefit of continuously conducting its mission in all-weather by loading a SAR (Synthetic Aperture Radar) payload. During IOT (In-Orbit Test) periods, calibration and validation campaign is performed to determine that bus and payload are working as expected. Differently the conventional corner reflector, active transponder has a capability to adjust internal gain to meet the pre-defined RCS. In this paper, design, integration and verification conducted as an effort to develop active transponder for KOMPSAT-5 mission were presented. View full abstract»

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