Indeed, this is the greatest enemy of our times, one that we need to recognize and fight before we lose a battle that we did not foresee. To counter this imminent threat, we propose a new post-war role for the US military in a global environmental defense initiative in which our military capabilities would be restructured into a planetary environmental defense force. Dea; Peder M. The acoustic complementary spectral regions are identified as Infrasonic.
Free Polarimetric Radar Imaging: From Basics to Applications (Optical…
These low frequency waves play an important role in coupled lithospheric-ionospheric wave interaction especially in the upper ULF above. In this paper, an introduction to this exciting re-emerging field is presented, paying major emphasis on recent findings regarding the observation of elevated electromagnetic low frequency noise, strongly peaking in the 0. Also, polarimetric signatures resulting from the interaction of large space vehicles with the ionosphere will be discussed.
Radar and optical polarimetry: a comparative study Author s : John C. Hubbert; V. Chandrasekar ; Viswanathan N. Bringi Show Abstract. The fields of radar and optical polarimetry are compared. Both fields have defined scattering matrices that describe the coherent scattering of monochromatic electric fields. This paper compares the mathematics of the two disciplines by redeveloping Kennaugh's optimum polarization theory in the context of optical polarimetry.
In addition, a novel definition of 'eigenpolarization' is given. Ku-band polarization characteristics of crops and fallow Author s : Martin R. Hinds; George J. Sofko; A. Wacker; James A.
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Koehler Show Abstract. The system was used to evaluate the polarization response of three cereal crops spring wheat, durum wheat, and barley , canola and fallow fields. It was found that all the targets caused partial unpolarization a decrease in the polarization ratio of the transmitted state but no depolarization in that the polarized portion of the received signal had the same linear polarization as the transmitted state H or V.
As a consequence, one can recover all the polarization information about these targets from the standard scatterometer measurements. This can be stated as the 'Scatterometer Polarization Theorem', in which the co-polar scatterometer components HH or VV contain all the polarized power plus half the unpolarized power, while the cross-polar components HV or VH contain exactly half of the unpolarized power.
There was more attenuation by wheat of V than H transmissions. This indicates that, for the V transmit state, the polarized component of the signal is anti-correlated with the plant water content. For canola, a randomly structured target medium, the unpolarized component of the signal correlates positively with plant moisture. Some far-field radar imaging techniques like spotlight-mode synthetic aperture radar and holography are shown to have a tomographic formulation.
For short radar-target distance much shorter than the distance required in the far-field condition the far-field computer aided tomography algorithm CAT may blur the reconstructed image. After studying first the near- field theory of some microwave imaging techniques, this paper shows that a unified near-field microwave tomography algorithm is possible. The received signal in SAR, which is a convolution between the spherical projection of the target and the emitted signal, can be interpreted as a Fourier transform of the spherical projection of the image as in near-field holography and tomography.
Reconstruction of an SAR image may then be accomplished using a back projection algorithm. This study is an interchange of ideas between these different disciplines and it is a step towards a unified near-field algorithm. An optimal method can be used for combining the four polarimetric images hv basis to reduce speckle compared with the span image and single channel image.
Huynen's main contributions in the development of polarimetric radar techniques and how the 'Radar Targets Phenomenological Concept' becomes a theory Author s : Eric Pottier Show Abstract. This paper is dedicated to him, and it is a great honor for the author to present here a summary on some of the main Dr. This leads to three world-views. One is the world of basic symmetry we live in, while the other is applicable to an exotic world where there is a preference for helices with right sense.
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The other exotic world caters to a world composed of helices with left sense. Hence we have arrived at a unique N-target decomposition which caters to the world of basic symmetry we live in. In this world it is still possible to have helices of any kind, but predominantly the symmetry is preferred, i. Other types of decomposition are based on eigenvalues and eigentargets. These are not transparent in general as to their physical significance. All these physically based arguments lead us to conclude that the N-target decomposition is unique and physically realizable in all cases.
The paper gives an overview about the activities at DLR in the field of ground based polarimetric radar imaging. Some features of the measurement equipment are given. The basic principle of the generation of complex target microwave images from scattered fields is outlined, and the derivation of target characteristic parameters as well as target characteristic polarizations is described.
Special emphasis is given to the analysis of localized scattering centers. Two methods for studying bistatic scattering effects on a monostatic range are introduced. The physics of radar backscatter from randomly distributed targets is explained especially with respect to the measurement of scattering matrix time series. Further, the determination of signal degradations on Earth-satellite paths by means of the DLR weather radar is dealt with. Review and preview of wideband radar polarimetry conferences, workshops, and symposia Author s : Wolfgang-Martin Boerner Show Abstract.
A succint overview of basic events in the development of polarimetry--low frequency to optical regions--is followed by a succinct summary of the basic underlying principles of 'Direct and Inverse Methods in Polarimetry', including some pertinent examples. Geometrical concepts in optimal polarimetry: Stokes formalism in a Minkowski space Author s : David H. Bebbington Show Abstract. Geometrical concepts which have long been central to the Poincare sphere and Stokes vector representations are extended to include vector representations of target scattering matrices via a new derivation based on spinor algebra techniques.
New results include the geometric significance of an absolute target phase, an interpretation of Graves' power scattering matrix as a four-vector, and its relationship to the complex target vector. The mathematical and physical significances of the interpretation of Stokes vector space as having a Minkowskian geometry are discussed. The consequences of Lorentz invariance are explored in an application to incoherent backscatter optimal polarimetry. Basic principles of radar polarimetry are introduced and various optimization procedures for the propagation scattering range operator equation and the received power expressions are presented and compared.
The characteristic polarization theory for the monostatic reciprocal coherent case in the cross- polarized radar channel is developed using a Stokes vector formalism. Power representation in terms of the Stokes vector and the Mueller matrix is utilized to determine the characteristic polarization states for optimal reception of the coherent wave.
The optimization procedure for the channel power leads to an eigenvalue equation which explains the characteristic polarization state properties mathematically and physically. A total of six theoretical characteristic polarization states for a single target can be derived by this method.
Polarimetric Radar Imaging : From Basics to Applications
Several target examples are considered to show a perfect agreement with the results obtained by an alternative method of using the polarization transformation ratio formulation for the coherent Sinclair matrix. Application of Cloude's target decomposition theorem to polarimetric imaging radar data Author s : Jakob J. In this paper we applied Cloude's decomposition to imaging radar polarimetry. We show in detail how the decomposition results can guide the interpretation of scattering from vegetated area. For multi-frequency polarimetric radar measurements of a clearcut area, the decomposition leads us to conclude that the vegetation is probably thin compared to even the C-band radar wavelength of 6 cm.
For a forested area, we notice an increased amount of even number of reflection scattering at P-band and L-band, probably the result of penetration through the coniferous canopy resulting in trunk-ground double reflection scattering.
Polarimetric Radar Imaging : From basics to applications.
The scattering for the forested area is still dominated by scattering from randomly oriented cylinders, however. It is found that these cylinders are thicker than in the case of clearcut areas, leading us to conclude that scattering from the branches probably dominate in this case. Polarization effects in nearfield radio wave sensing of buried anomalies Author s : W. Davis; James T. Nilles; Gus P. Tricoles Show Abstract.
The nearfield reflectance of a buried, dielectric object of circular shape was measured with an antenna operating in its and the object's nearfield region for two orthogonal linear polarizations. Reflectance depended on polarization. Mutual coupling between individual antennas was also measured and found to depend on polarization. Interpolation procedure to construct complete polarimetric signature of distributed targets from switched polarization measurements Author s : V.
Chandrasekar ; John C. Hubbert; Viswanathan N. Bringi; Peter F. Meischner Show Abstract. A fully polarimetric radar system consists of orthogonal dual polarized transmission mode and a dual channel receive mode that are typically set to be copolar and cross polar to the transmit state of polarization. The transmit polarization state can be switched alternately between the two states. Carefully and meticulously updated in each iteration, the book continues to be the most comprehensive scanning Suitable as either a student text or professional reference, Lightwave Engineering addresses the behavior of electromagnetic waves and the propagation of light, which forms the basis of the wide-ranging field of optoelectronics.
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