Showing papers on "Polarimetry published in 2005"
TL;DR: The polarization uniqueness in transmission of this mixed basis mode, hereafter referred to as the /spl pi//4 mode, maintains the standard lower pulse repetition frequency operation and hence maximizes the coverage of the sensor.
Abstract: We assess the performance of synthetic aperture radar (SAR) compact polarimetry architectures based on mixed basis measurements, where the transmitter polarization is either circular or orientated at 45/spl deg/(/spl pi//4), and the receivers are at horizontal and vertical polarizations with respect to the radar line of sight. An original algorithm is proposed to reconstruct the full polarimetric (FP) information from this architecture. The performance assessment is twofold: it first concerns the level of information preserved in comparison with FP, both for point target analysis and crop fields classification, using L-band SIRC/XSAR images acquired over Landes forest and Jet Propulsion Laboratory AIRSAR images acquired over Flevoland. Then, it addresses the space implementation complexity, in terms of processed swath, downloading features, power budget, calibration, and ionospheric effects. The polarization uniqueness in transmission of this mixed basis mode, hereafter referred to as the /spl pi//4 mode, maintains the standard lower pulse repetition frequency operation and hence maximizes the coverage of the sensor. Because of the mismatch between transmitter and receiver basis, the power budget is deteriorated by a factor of 3 dB, but it can partly be compensated.
322 citations
TL;DR: In this article, a self-consistent method for rain attenuation of radar reflectivity and differential reflectivity at the X-band wavelength is presented, which was originally developed and evaluated for C-band polarimetric radar data.
Abstract: In this two-part paper, a correction for rain attenuation of radar reflectivity (ZH) and differential reflectivity (ZDR) at the X-band wavelength is presented. The correction algorithm that is used is based on the self-consistent method with constraints proposed by Bringi et al., which was originally developed and evaluated for C-band polarimetric radar data. The self-consistent method is modified for the X-band frequency and is applied to radar measurements made with the multiparameter radar at the X-band wavelength (MP-X) operated by the National Research Institute for Earth Science and Disaster Prevention (NIED) in Japan. In this paper, characteristic properties of relations among polarimetric variables, such as AH–KDP, ADP–AH, AH–ZH, and ZDR–ZH, that are required in the correction methodology are presented for the frequency of the MP-X radar (9.375 GHz), based on scattering simulations using drop spectra measured by disdrometers at the surface. The scattering simulations were performed under ...
195 citations
TL;DR: An analysis of measurements of the normalized radar cross-section (NRCS) in vertical and horizontal polarizations over the ocean obtained from the C-band airborne radar STORM, finding the polarization ratio to be dependent on incidence and azimuth angles.
Abstract: This paper presents an analysis of measurements of the normalized radar cross-section (NRCS) in vertical and horizontal polarizations over the ocean obtained from the C-band airborne radar STORM. The dataset was collected during the experiment called "Validation with a Polarimetric Airborne Radar of ENVISAT SAR over the Ocean (VALPARESO)", which took place during the calibration/validation phase of the ENVISAT Advanced Synthetic Aperture Radar (ASAR). From this dataset, the properties of the polarization ratio are discussed and in particular its dependencies with radar geometry (incidence and azimuth angle) as well as with meteorological conditions (wind and sea state). The polarization ratio is found to be dependent on incidence and azimuth angles. Its dependence with incidence angle is found to be significantly different from empirical models previously proposed in the literature. It also exhibits some correlation with surface conditions (wind and wave) with a more important correlation with significant wave steepness. Two new analytical formulations are proposed to model the polarization ratio, one as a function of incidence angle only, the second one with additional dependence with azimuth angle. It is shown that it is necessary to consider an azimuth-dependent polarization ratio for incidence angles larger than 30/spl deg/. Comparisons with the polarization ratio from ENVISAT ASAR images are used to assess this model.
179 citations
TL;DR: A novel estimator for the eigenvalues of the covariance or coherency matrix is proposed to reduce the biases for a small number of averaged samples in the estimation of physical information in radar polarimetry.
Abstract: The performance of quantitative remote sensing based on multidimensional synthetic aperture radars (SARs), and polarimetric SAR systems in particular, depends strongly on a correct statistical characterization of the data, i.e., on a complete knowledge of the effects of the speckle noise. In this framework, the eigendecomposition of the covariance or coherency matrices and the associated H//spl alpha/_/A decomposition have demonstrated the potential for quantitative estimation of physical parameters. In this paper, we present a detailed study of the statistics associated with this decomposition. This analysis requires the introduction of mathematical tools that are not well known in the remote sensing community. For this reason, we include a review section to present them. Using this work, we then present an expression for the probability density function of the sample eigenvalues of the covariance or coherency matrix. The availability of this expression allows a complete study of the separated sample eigenvalues, as well as, the entropy H and the anisotropy A. As demonstrated, all these parameters must be considered as asymptotically nonbiased with respect to the number of looks. In order to reduce the biases for a small number of averaged samples, a novel estimator for the eigenvalues is proposed. The results of this work are analyzed by means of simulated and real airborne SAR data. This analysis permits us to determine in detail the effects of the number of averaged samples in the estimation of physical information in radar polarimetry.
128 citations
TL;DR: In this article, a method for high-sensitivity birefringence quantification by using enhanced polarization-sensitive optical coherence tomography (EPS-OCT) is presented.
Abstract: Polarization-sensitive optical coherence tomography provides high-resolution cross-sectional characterization of birefringence in turbid media. Weakly birefringent biological tissues such as the retinal nerve fiber layer (RNFL) require advanced speckle noise reduction for high-sensitivity measurement of form birefringence. We present a novel method for high-sensitivity birefringence quantification by using enhanced polarization-sensitive optical coherence tomography (EPS-OCT) and introduce the polarimetric signal-to-noise ratio, a mathematical tool for analyzing speckle noise in polarimetry. Multiple incident polarization states and nonlinear fitting of normalized Stokes vectors allow determination of retardation with ±1° uncertainty with invariance to unknown unitary polarization transformations. Results from a weakly birefringent turbid film and in vivo primate RNFL are presented. In addition, we discuss the potential of EPS-OCT for noninvasive quantification of intracellular filamentous nanostructures, such as neurotubules in the RNFL that are lost during the progression of glaucoma.
124 citations
TL;DR: In this paper, a divided aperture MWIR imaging polarimeter is proposed to acquire multiple polarization images simultaneously from a single focal plane array from an image relay lens set, each of which measures a different orientation of linear polarization.
Abstract: Imaging polarimetry has the potential to be a key sensor technology in a number of target detection applications. Imaging polarimeters measure the polarization state of light emitted from and/or reflected from scenes. The light is polarized because of the geometry, roughness and material properties of the objects embedded in the scene. This added information enhances conventional intensity and color imagery, potentially surpassing its performance in low contrast situations. In this paper, we describe a divided aperture MWIR imaging polarimeter which acquires multiple polarization images simultaneously. At the heart of the polarimeter is a relay lens set that produces four identical images on a single focal plane array from a single aperture. Each of the four images measures a different orientation of linear polarization, 0, 45, 90 and 135 degrees. The relay lens set operates inside of a pour fill Dewar of a InSb MWIR camera. The design and calibration method for the polarimeter are given along with example data sets taken from the air over Huntsville, AL.
106 citations
TL;DR: In this paper, a model for the German Vacuum Tower Telescope (VTT) that describes its time-dependent polarization properties is presented, based on a Mueller matrix that depends on the geometry of the light beam through the telescope, and on material properties.
Abstract: It is essential to properly calibrate the polarimetric properties of telescopes, if one wants to take advantage of the capabilities of high precision speclro-polarimeters. We have constructed a model for the German Vacuum Tower Telescope (VTT) that describes its time-dependent polarization properties. Since the coeloslat of the telescope changes the polarization state of the light by introducing cross talk among different polarization states, such a model is necessary to correct the measurements, in order to retrieve the true polarization as emitted from the Sun. The telescope model is quantified by a time-dependent Mueller matrix that depends on the geometry of the light beam through the telescope, and on material properties: the refractive indices of the coclostal mirrors, and the birefringence of the entrance window to the vacuum tube. These material properties were determined experimentally in-situ by feeding the telescope with known states of polarization (including unpolarized light) and by measuring its response. and from measurements of an aluminum-coated sample in the laboratory. Accuracy can in our case be determined only for the combinalion of telescope and spectro-polarimeter used: for the instrument POLIS at the VTT, we estimate an accuracy of ±4-5 x 10 -3 for the cross talk correction coefficients.
97 citations
TL;DR: The novel concept of a phase tube is introduced which enables a quantitative assessment of the Pol-InSAR performance, a comparison between different sensor configurations, and an optimization of the instrument settings for different Pol-inSAR applications, which may serve as an interface between system engineers and application-oriented scientists.
Abstract: We investigate multichannel imaging radar systems employing coherent combinations of polarimetry and interferometry (Pol-InSAR). Such systems are well suited for the extraction of bio- and geophysical parameters by evaluating the combined scattering from surfaces and volumes. This combination leads to several important differences between the design of Pol-InSAR sensors and conventional single polarisation SAR interferometers. We first highlight these differences and then investigate the Pol-InSAR performance of two proposed spaceborne SAR systems (ALOS/PalSAR and TerraSAR-L) operating in repeat-pass mode. For this, we introduce the novel concept of a phase tube which enables (1) a quantitative assessment of the Pol-InSAR performance, (2) a comparison between different sensor configurations, and (3) an optimization of the instrument settings for different Pol-InSAR applications. The phase tube may hence serve as an interface between system engineers and application-oriented scientists. The performance analysis reveals major limitations for even moderate levels of temporal decorrelation. Such deteriorations may be avoided in single-pass sensor configurations and we demonstrate the potential benefits from the use of future bi- and multistatic SAR interferometers.
80 citations
TL;DR: SPINOR as mentioned in this paper is a spectro-polarimeter that will serve as a facility instrument for the Dunn Solar Telescope at the National Solar Observatory, which is capable of achromatic polarimetry over a very broad range of wavelengths, from 430 up to 1600 nm, allowing for the simultaneous observation of several visible and infrared spectral regions with full Stokes polarimmetry.
Abstract: SPINOR is a new spectro-polarimeter that will serve as a facility instrument for the Dunn Solar Telescope at the National Solar Observatory. This instrument is capable of achromatic polarimetry over a very broad range of wavelengths, from 430 up to 1600 nm, allowing for the simultaneous observation of several visible and infrared spectral regions with full Stokes polarimetry. Another key feature of the design is its flexibility to observe virtually any combination of spectral lines, limited only by practical considerations (e.g., the number of detectors available, space on the optical bench, etc).
73 citations
TL;DR: This work reports a novel approach for characterizing the polarization properties of electromagnetic fields for which the electric field vector at a point may fluctuate in three dimensions, using probes which couple all three components of the field.
Abstract: The state of polarization of an optical field provides detailed information concerning both the radiation emission processes and the intricate interaction between light and matter. We report here a novel approach for characterizing the polarization properties of electromagnetic fields for which the electric field vector at a point may fluctuate in three dimensions. Using probes which couple all three components of the field, we were able to extract the polarized and unpolarized components of such fields. Our results constitute the proof of concept for what could be called three-dimensional optical polarimetry.
19 May 2005
TL;DR: In this article, a novel polarimetric millimeter-wave imaging technique has been developed at the Pacific Northwest National Laboratory (PNNL) for concealed weapon detection applications, where three-dimensional images are formed using computer image reconstruction algorithms developed to mathematically focus the received wavefronts scattered from the target.
Abstract: A novel polarimetric millimeter-wave imaging technique has been developed at the Pacific Northwest National Laboratory (PNNL) for concealed weapon detection applications. Wideband millimeter-wave imaging systems developed at PNNL utilize low-power, coherent, millimeter-wave illumination in the 10-100 GHz range to form high-resolution images of personnel. Electromagnetic waves in these frequency ranges easily penetrate most clothing materials and are reflected from the body and any concealed items. Three-dimensional images are formed using computer image reconstruction algorithms developed to mathematically focus the received wavefronts scattered from the target. Circular polarimetric imaging can be employed to obtain additional information from the target. Circularly polarized waves incident on relatively smooth reflecting targets are typically reversed in their rotational handedness, e.g. left-hand circular polarization (LHCP) is reflected to become right-hand circular polarization (RHCP). An incident wave that is reflected twice (or any even number) of times prior to returning to the transceiver, has its handedness preserved. Sharp features such as wires and edges tend to return linear polarization, which can be considered to be a sum of both LHCP and RHCP. These characteristics can be exploited for personnel screening by allowing differentiation of smooth features, such as the body, and sharper features present in many concealed items. Additionally, imaging artifacts due to multipath can be identified and eliminated. Laboratory imaging results have been obtained in the 10-20 GHz frequency range and are presented in this paper.
TL;DR: An approach to image the polarization state of object points in a wide field of view, while enhancing the radiometric dynamic range of imaging systems by generalizing image mosaicing, which is biologically inspired, as it emulates spatially varying polarization sensitivity of some animals.
Abstract: We present an approach to image the polarization state of object points in a wide field of view, while enhancing the radiometric dynamic range of imaging systems by generalizing image mosaicing. The approach is biologically inspired, as it emulates spatially varying polarization sensitivity of some animals. In our method, a spatially varying polarization and attenuation filter is rigidly attached to a camera. As the system moves, it senses each scene point multiple times, each time filtering it through a different filter polarizing angle, polarizance, and transmittance. Polarization is an additional dimension of the generalized mosaicing paradigm, which has recently yielded high dynamic range images and multispectral images in a wide field of view using other kinds of filters. The image acquisition is as easy as in traditional image mosaics. The computational algorithm can easily handle nonideal polarization filters (partial polarizers), variable exposures, and saturation in a single framework. The resulting mosaic represents the polarization state at each scene point. Using data acquired by this method, we demonstrate attenuation and enhancement of specular reflections and semi reflection separation in an image mosaic.
TL;DR: In this article, the authors present results of imaging and aperture polarimetry of the dust of comet 2P/Encke at phase angles 91-105°, obtained during the 2003 apparition.
Abstract: We present results of imaging and aperture polarimetry of the dust of comet 2P/Encke at phase angles 91–105°, obtained during the 2003 apparition. We investigate how strongly molecular emissions transmitted by the filters used in the observations can affect the resulting polarization of cometary dust. This problem is of particular importance for so-called gas-rich comets like comet 2P/Encke which has particularly strong molecular emission as compared to its dust continuum. Aperture polarimetry in the wide-band UBVR filters was performed at the 2.6-m Shain telescope and 1.25-m telescope of the Crimean Astrophysical Observatory on November 17–24. From these measurements a dust polarization of ≈ % is derived, which puts the comet in the class of comets with low polarization. The imaging observations of comet 2P/Encke were carried out at the 2-m telescope of the Bulgarian National Astronomical Observatory on November 20–22, 2003. Narrow-band filters centered on the 0–7–0 transition of the A 2A_1 – 2B_1 electronic band system of NH2 (662 nm) and on an adjacent red continuum at 642 nm were employed. The polarization of NH2 averaged over the 0–7–0 vibronic transition amounts to ≈ % at phase angles close 90°, similar to the polarization of the two-atomic molecules CN and C2 . The dust polarization however, when corrected for the effect of molecular emissions, is larger than 30%. We conclude that the division of comets into two polarimetric classes with one class having in the visual wavelength range a maximum polarization less than 20% is caused by ignoring the contribution of molecular emission and therefore is an artifact. Whether the comet displays a strong silicate feature (i.e. its dust grains are small) or not, the dust polarization is high.
TL;DR: In this article, a fully polarimetric two-dimensional (2D) time-frequency analysis method is introduced to decompose processed SAR images into range-frequency and azimuth-frequency domains.
Abstract: In synthetic aperture radar (SAR) polarimetry, it is generally assumed that the sensor has a fixed orientation with respect to objects and illuminates a scene with monochromatic radiations. Modern high-resolution SAR sensors have a wide azimuth beam width, however, and a large bandwidth in range. During SAR image formation, multiple squint angles and radar wavelengths are integrated to synthesize the full-resolution SAR image, and variations in the polarimetric signatures due to changes in the azimuthal look angle and in the wavelength commonly remain unconsidered. In this paper, a fully polarimetric two-dimensional (2D) time–frequency analysis method is introduced to decompose processed polarimetric SAR images into range–frequency and azimuth–frequency domains. This 2D representation permits characterization of the frequency response of the scene reflectivity, observed under different azimuth look angles and wavelengths. For the case of Bragg resonance in agricultural areas, the influence of anisotropic ...
TL;DR: In this article, a microwave-based method to make images of fiber structure, e.g., to locate knots in wood, was presented, and experiments support the theoretical evaluation showing that knots can be followed in images of polarimetric parameters.
Abstract: In this paper, we present a new microwave-based method to make images of fiber structure, e.g., to locate knots in wood. Evaluation of Maxwell's equations for an electromagnetic wave propagating in an anisotropic media (wood) shows that the polarization of the wave depends on the local fiber orientation in the sample. Experiments support the theoretical evaluation showing that knots can be followed in images of polarimetric parameters, reconstructed from multiple monostatic measurements. The equipment works at low intensity and is, therefore, virtually harmless to human beings; furthermore, it can be made portable and be operated by a single person.
TL;DR: The results show that the performance of a wire-grid polarizer evaluated in transmittance and extinction ratio is substantially degraded with rotation, although it is still more robust than that of a perfect polarizer.
Abstract: I explore the polarization characteristics of a wire-grid polarizer operating in a rotating platform using well-established rigorous coupled-wave analysis. The results show that the performance of a wire-grid polarizer evaluated in transmittance and extinction ratio is substantially degraded with rotation, although it is still more robust than that of a perfect polarizer. The performance may further deteriorate with inclined incidence due to an increased negative effect of a Rayleigh anomaly. Either a finer or a deeper grating reduces the adverse effect of rotation. Although implementation of such a grating is difficult, the rotation characteristics can be enhanced by means of pixelating the wire grids of various orientations and capturing the input images with a sufficiently high sampling rate.
11 Jan 2005
TL;DR: A pushbroom multi-camera architecture is envisioned, using separate line arrays to collect imagery within each camera in the different spectral bands and in different polarization orientations, to achieve climate-quality uncertainties in optical depth, refractive index, and other microphysical properties.
Abstract: Techniques for passive remote sensing of aerosol optical and microphysical properties from space include visible, near- and shortwave-infrared imaging (e.g., from MODIS), multiangle intensity imaging (e.g., ATSR-2, AATSR, MISR), near-ultraviolet mapping (e.g., TOMS/OMI), and polarimetry (e.g., POLDER, APS). Each of these methods has unique strengths. In this paper, we present a concept for integrating these approaches into a unified sensor. Design goals include spectral coverage from the near-UV to the shortwave infrared; intensity and polarimetric imaging simultaneously at multiple view angles; global coverage within a few days; kilometer to sub-kilometer spatial resolution; and measurement of the degree of linear polarization (DOLP) for a subset of the spectral complement with an uncertainty of 0.5% or less. This high polarimetric accuracy is the most challenging aspect of the design, and is specified in order to achieve climate-quality uncertainties in optical depth, refractive index, and other microphysical properties. Based upon MISR heritage, a pushbroom multi-camera architecture is envisioned, using separate line arrays to collect imagery within each camera in the different spectral bands and in different polarization orientations. For the polarimetric data, accurate cross-calibration of the individual line arrays is essential. An electro-optic polarization "scrambler", activated periodically during calibration sequences, is proposed as a means of providing this cross-calibration. The enabling component is a rapid retardance modulator. Candidate technologies include liquid crystals, rotating waveplates, and photoelastic modulators (PEMs). The PEM, which uses a piezoelectric transducer to induce rapid time-varying stress birefringence in a glass bar, appears to be the most suitable approach. An alternative measurement approach, also making use of a PEM, involves synchronous demodulation of the oscillating signal to reconstruct the polarization state. The latter method is potentially more accurate, but requires a significantly more complex detector architecture.
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28 Sep 2005TL;DR: In this paper, a calibration operation is performed using a symmetrical radar reflector, to determine the gains and phases of reception of two mutually orthogonal components of the received reflected signal which result in nulling of the two polarization components.
Abstract: A polarimetric radar system transmits a signal which is nominally the desired polarization, but which may deviate therefrom. A calibration operation is performed using a symmetrical radar reflector, to determine the gains and phases of reception of two mutually orthogonal components of the received reflected signal which result in nulling of the two polarization components of the reflected signal. These gains and phases represent receive corrections which result in a simulation of perfect polarization purity on both transmission and reception. The corrections established during calibration are applied to the receive signals during normal (non-calibration) operation, to improve the effective polarization of the transmission and reception.
11 Oct 2005-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a Compton polarimeter based on a Fabry-Perot cavity photon beam amplifier was used for beam polarization measurement at Jlab Hall A. At an electron energy of 4.6 GeV and a beam current of 40 μ A, a total relative uncertainty of 1.5% was achieved within 40min of data taking.
Abstract: A major advance in accurate electron beam polarization measurement has been achieved at Jlab Hall A with a Compton polarimeter based on a Fabry–Perot cavity photon beam amplifier. At an electron energy of 4.6 GeV and a beam current of 40 μ A, a total relative uncertainty of 1.5% is typically achieved within 40 min of data taking. Under the same conditions monitoring of the polarization is accurate at a level of 1%. These unprecedented results make Compton polarimetry an essential tool for modern parity-violation experiments, which require very accurate electron beam polarization measurements.
01 Oct 2005
TL;DR: In this paper, the expected polarization properties of extra-solar planets are discussed that can be inferred from polarimetry of “our” solar system planets, and the results from a phase A (feasibility) study for a polarimetric arm in the ESO VLT planet finder instrument are presented.
Abstract: Light reflected from planets is polarized. This basic property of planets provides the possibility for detecting and characterizing extra-solar planets using polarimetry. The expected polarization properties of extra-solar planets are discussed that can be inferred from polarimetry of “our” solar system planets. They show a large variety of characteristics depending on the atmospheric and/or surface properties. Best candidates for a polarimetric detection are extra-solar planets with an optically thick Rayleigh scattering layer.Even the detection of highly polarized extra-solar planets requires a very sophisticated instrument. We present the results from a phase A (feasibility) study for a polarimetric arm in the ESO VLT planet finder instrument. It is shown that giant planets around nearby stars can be searched and investigated with an imaging polarimeter, combined with a powerful AO system and a coronagraph at an 8 m class telescope.A similar type of polarimeter is also considered for the direct detection of terrestrial planets using an AO system on one of the future Extremely Large Telescopes.
27 Oct 2005
TL;DR: The results suggest that the design of a wire-grid polarizer used in imaging polarimetry avoids incurring a Rayleigh anomaly, which causes a substantial increase in polarimetric nonuniformity.
Abstract: The polarimetric performance nonuniformity of a wire-grid polarizer (WGP) used in imaging polarimetry is investigated with a simple numerical model. The simulation results based on rigorous coupled-wave analysis show that the aperture ratio between the entrance pupil and the WGP significantly affects the uniformity among pixels of a WGP. Even with a WGP smaller than an imaging aperture, the results suggest that the design avoids incurring a Rayleigh anomaly, which causes a substantial increase in polarimetric nonuniformity. Minimizing the variation due to the characteristics of a WGP is important to reduce the likelihood of an error in imaging polarimetry.
TL;DR: A broadband wavelength-parallel polarimeter has been designed or polarization measurements of multiple Dense WDM channels in parallel, which is based on a 2-D spectral disperser via a diffraction grating and a virtually-imaged phased-array.
Abstract: A broadband wavelength-parallel polarimeter has been designed for polarization measurements of multiple Dense WDM channels in parallel, which is based on a 2-D spectral disperser via a diffraction grating and a virtually-imaged phased-array (VIPA). At a hyperfine 2.8 GHz subchannel spacing, we have demonstrated spectral polarization measurements of ~1500 sub-channels (~32 nm spectral range), with a potential total measurement time of less than 5 ms.
TL;DR: Spherical neutron polarimetry provides a new tool for the study of magneto-electric crystals since it allows the rotation of scattered polarisation, characteristic of this class of crystal to be measured.
TL;DR: A new coherence optimization algorithm is proposed for polarimetric synthetic aperture radar (SAR) interferometry applications by using the polarization state conformation algorithm based on the polarIMetric basis transformation along with the polarization signatures to maximize the resemblance between the scattering mechanisms of the same target in the repeat-pass POLSAR images.
Abstract: A new coherence optimization algorithm is proposed for polarimetric synthetic aperture radar (SAR) interferometry applications by using the polarization state conformation algorithm based on the polarimetric basis transformation along with the polarization signatures. Through application of this algorithm, the resemblance between the scattering mechanisms of the same target in the repeat-pass polarimetric SAR (POLSAR) images is maximized. Then, coherence maps between the repeat-pass POLSAR images, before and after application of the algorithm, are generated. The coherences obtained by this method represent the best coherences or optimized coherences between the POLSAR images. The effects predicted by the theory are confirmed by the POLSAR data acquired by the Jet Propulsion Laboratory Spaceborne Imaging Radar mission.
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12 Jan 2005TL;DR: In this article, a system and method for compensating for the effects of birefringence in a given sample and employing an optical birerer to sense the real-time bireringence contributions and then providing a feedback signal to a compound electro-optical system that negates the birefine contributions found in the given sample.
Abstract: The present invention relates to a system and method for compensating for the effects of birefringence in a given sample and employs an optical birefringence analyzer to sense the real-time birefringence contributions and then provides a feedback signal to a compound electro-optical system that negates the birefringence contributions found in the given sample. The birefringence contribution vanishes, thus significantly reducing the main error component for polarimetric measurements.
25 Jul 2005
TL;DR: This paper reviews theoretical work carried out in collaboration with Dr Luneburg during a sabbatical period with him in 1997 and concentrates on the exploitation of coherent polarimetry effects in bistatic geometries and on the partially coherent case by considering how the entropy/alpha approach can be modified for use in bISTatic scenarios.
Abstract: In this paper, presented in the Ernst Luneburg memorial session, we first review theoretical work carried out in collaboration with Dr Luneburg during a sabbatical period with him in 1997. We then up-date progress in the area of bistatic polarimetry theory and concentrate on two main areas, on the exploitation of coherent polarimetry effects in bistatic geometries and then on the partially coherent case by considering how the entropy/alpha approach can be modified for use in bistatic scenarios.
TL;DR: In this paper, the authors reported results of polarimetric imaging observations of Mars with the Hubble Space Telescope during the 2003 opposition and discovered transient polarization phenomena interpreted as clouds that are best observed in ultraviolet light.
01 Jan 2005
TL;DR: In this article, a methodology based on least squares adjustment of tie point and ground control point observations in a multi-temporal SAR mosaic dataset was used to produce a tie point RMSE (Root Mean Square Error) of 56 m and a GCP RMSE of 240 m in the African mosaic of the GRFM (Global Rain Forest Mapping) project.
Abstract: Aspects of forest biomass mapping using SAR (Synthetic Aperture Radar) data were studied in study sites in northern Sweden, Germany, and south-eastern Finland. Terrain topography – via the area of a resolution cell – accounted for 61 percent of the total variation in a Seasat (L-band) SAR scene in a hilly and mountainous study site. A methodology – based on least squares adjustment of tie point and ground control point observations in a multi-temporal SAR mosaic dataset – produced a tie point RMSE (Root Mean Square Error) of 56 m and a GCP RMSE of 240 m in the African mosaic of the GRFM (Global Rain Forest Mapping) project. The mosaic consisted of 3624 JERS SAR scenes. A calibration revision methodology – also based on least squares adjustment and points in overlap areas between scenes – removed a calibration artifact of about 1 dB. A systematic search of the highest correlation between forest stem volume and backscattering amplitude was conducted over all combinations of transmit and receive polarisations in three AIRSAR scenes in a German study site. In the P-band, a high and narrow peak around HV-polarisation was found, where the correlation coefficient was 0.75, 0.59, and 0.71 in scenes acquired in August 1989, June 1991, and July 1991, respectively. In other polarisations of P-band, the correlation coefficient was lower. In L-band, the polarisation response was more flat and correlations lower, between 0.54 and 0.70 for stands with a stem volume 100 m/ha or less. Three summer-time JERS SAR scenes produced very similar regression models between forest stem volume and backscattering amplitude in a study site in south-eastern Finland. A model was proposed for wide area biomass mapping when biomass accuracy requirements are not high. A multi-date regression model employing three summer scenes and three winter scenes produced a multiple correlation coefficient of 0.85 and a stem volume estimation RMSE of 41.3m/ha. JERS SAR scenes that were acquired in cold winter conditions produced very low correlations between stem volume and backscattering amplitude.