Showing papers on "Polarimetry published in 1991"
01 Nov 1991
TL;DR: A tutorial review of the broad sweep of topics relating to imaging radar polarimetry, ranging from mathematical foundations to hardware and from implementation approaches to signal processing and calibration, is presented.
Abstract: Presents a tutorial review of the broad sweep of topics relating to imaging radar polarimetry, ranging from mathematical foundations to hardware and from implementation approaches to signal processing and calibration. The authors examine current developments in sensor technology and implementation for recording polarimetric measurements, and describe techniques and areas of application for this form of remotely sensed data. Those aspects of ground signal processing and calibration peculiar to the polarimetric signals are addressed. Several of the currently operating instruments and some of the implementations planned for future use are discussed. >
218 citations
TL;DR: A polarimetric radar calibration procedure is introduced and verified with experimental results that is useful for some single antenna systems and has the advantage that only two known targets are required.
Abstract: A polarimetric radar calibration procedure is introduced and verified with experimental results. The procedure requires measurements of three known targets in order to determine the distortion matrices that characterize the effect of the measurement system on the transmitted and received waves. The scattering matrices for the known targets can be of any form, provided that a limited set of constraints is satisfied. A special case, wherein the transmit and receive distortion matrices are the transpose of each other, is considered. This case is useful for some single antenna systems and has the advantage that only two known targets are required. >
133 citations
01 Oct 1991
TL;DR: In this article, the target characteristic polarization state theory is developed for the coherent case using the three stage, the basis transformation, and the power (Mueller) matrix optimization procedures.
Abstract: Basic principles of radar polarimetry are introduced. The target characteristic polarization state theory is developed first for the coherent case using the three stage, the basis transformation, and the power (Mueller) matrix optimization procedures. Kennaugh's and Huynen's theories of radar target polarimetry are verified for the monostatic reciprocal case. It is shown that there exist, in total, five unique pairs of characteristic polarization states for the symmetric scattering matrix of which two pairs, the cross-polarization null and copolarization max pairs, are identical, whereas the cross-pol max and the cross-pol saddlepoint pairs are distinct. The theory is verified by an example for which next to the polarization fork the copolarized and cross-polarized power density plots are also presented. The partially polarized case for completely polarized wave incidence is presented and compared with the results for the coherent and the partially coherent cases, the latter of which is still unresolved. >
111 citations
TL;DR: In this article, the authors extended the concept of polarimetry in active remote sensing to passive remote sensing and demonstrated the potential use of the third and fourth Stokes parameters U and V for passive sensing by using the reciprocity principle.
Abstract: The concept of polarimetry in active remote sensing is extended to passive remote sensing The potential use of the third and fourth Stokes parameters U and V, which play an important role in polarimetric active remote sensing, is demonstrated for passive remote sensing It is shown that, by the use of the reciprocity principle, the polarimetric parameters of passive remote sensing can be obtained through the solution of the associated direct scattering problem These ideas are applied to study polarimetric passive remote sensing of periodic surfaces The solution of the direct scattering problem is obtained by an integral equation formulation which involves evaluation of periodic Green's functions and normal derivative of those on the surface Rapid evaluation of the slowly convergent series associated with these functions is observed to be critical for the feasibility of the method New formulas, which are rapidly convergent, are derived for the calculation of these series The study has shown that the brightness temperature of the Stokes parameter U can be significant in passive remote sensing Values as high as 50 K are observed for certain configurations
75 citations
TL;DR: In this article, an interpretation of the SN 1987A polarimetric data in terms of simple shape asymmetry requires that SN 1987a have a length-width difference of order 10 percent or more.
Abstract: Models and a polarized radiative transfer technique useful for analyzing the SN 1987A polarimetric data are introduced and discussed. Demonstration results calculated using the models are presented. An interstellar polarization correction needed for analyzing the SN 1987A polarimetric data is introduced. A summary and interpretation of the evolution of the SN 1987A polarization that relies on this correction is given. An analysis of a small selection of the SN 1987A polarimetry is reported. The important conclusions of this analysis are that the SN 1987A continuum polarization and line polarization features are mostly due to the polarizing effect of electron scattering and that there is probably an excitation asymmetry in SN 1987A. An interpretation of the SN 1987A polarimetric data in terms of simple shape asymmetry requires that SN 1987A have a length-width difference of order 10 percent or more. 82 refs.
69 citations
TL;DR: A calibration procedure for imaging radar polarimeters was developed and applied to a set of images acquired by the NASA DC-8 multifrequency radar system, presenting the results of applying this technique to radar scenes of lava flows of varying roughness, temperate and tropical rain forests, and ocean water surfaces.
Abstract: The authors developed a calibration procedure for imaging radar polarimeters and applied it to a set of images acquired by the NASA DC-8 multifrequency radar system. The technique requires the use of ground reflectors of known cross-section for absolute calibration, that is, solution for sigma /sup 0/; however, the image data themselves can usually provide all information necessary for phase calibration and for antenna crosstalk correction. The accuracy of the approach, as measured by calculating the cross-section residuals of known targets in each calibrated scene, is on the order of +or-1-2 dB at the P- and C-band, but improves to +or-0.5 dB at the L-band. The authors present the results of applying this technique to radar scenes of lava flows of varying roughness, temperate and tropical rain forests, and ocean water surfaces. They also present several example applications which are feasible with calibrated data but which would be difficult to implement with uncalibrated data. >
62 citations
TL;DR: In this paper, the authors make theoretical calculations of brightness temperatures of the third and fourth Stokes parameters for geophysical terrain based on vector radiative transfer theory with emission vector for random discrete scatterers.
Abstract: Recently there has been growing interest in the application of polarimetry to active microwave remote sensing of geophysical terrain. However, for passive microwave remote sensing, the third and fourth Stokes parameters were usually neglected in the past. In this paper, we make theoretical calculations of brightness temperatures of the third and fourth Stokes parameters for geophysical terrain. The calculations are based on vector radiative transfer theory with emission vector for random discrete scatterers. We also derive the reciprocal relations between emission of third and fourth Stokes parameters and the bistatic scattering coefficients for rough surface problems. Numerical results are illustrated. It is shown that brightness temperatures for third and fourth Stokes parameters can be as large as ±60°K for certain statistical asymmetrical configurations of scatterers.
56 citations
TL;DR: The University of Chicago far-infrared array polarimeter (STOKES) as discussed by the authors is the first multiple-beam polarimeter for far infrared astronomy, which is used to detect two orthogonal components of linear polarization.
Abstract: The University of Chicago far-infrared array polarimeter, 'STOKES', is the first multiple-beam polarimeter for far-infrared astronomy. Observations are made from the NASA Kuiper Airborne Observatory. Two orthogonal components of linear polarization are detected simultaneously by corresponding pairs of bolometers in two 32-detector arrays. Novel observing and data-analysis techniques are used to overcome the inherent difficulties of array polarimetry. Results from the first observing flights with the new instrument are reported for the molecular clouds W3 and W51. The measurements show that the magnetic-field structure in both clouds is nonuniform on the scale of 0.5-1.5 pc. This is consistent with molecular line and Zeeman observations that indicate the presence of turbulent velocities and significant small-scale structure. Preliminary results from the second flight series have yielded approximately 40 new measurements in the Sgr A complex. These results indicate that modifications made since the first flights have significantly improved the performance of STOKES.
54 citations
TL;DR: A discussion is presented of quantitative expressions required for the response of a synthetic aperture radar (SAR) to both point and distributed scatterers for purposes such as calibration and polarimetry.
Abstract: A discussion is presented of quantitative expressions required for the response of a synthetic aperture radar (SAR) to both point and distributed scatterers for purposes such as calibration and polarimetry. Image gains depend on the viewing geometry, which is unlike the flat Earth case, which often is assumed to apply in an orbital geometry. Image signal-to-noise ratio is dependent on footprint velocity, but the mean clutter-to-noise ratio for distributed scatterers is dependent on spacecraft velocity. When imagery of a distributed scene observed by an orbital SAR is to be calibrated by comparison to the impulse response of a reference point scatterer, for example, the velocity ratio enters the expression for peak power, but does not enter when an integral is used over the impulse response. The author also looks at the processing gain resulting from overlapping image pixels in azimuth through sampling of the pulse repetition frequency. >
50 citations
TL;DR: In this article, a catalog of SN 1987A polarimetry is given that covers the period from day 2 to day 262, including broad-band and narrow-band polarimetric and spectropolarimetry.
Abstract: A catalog of SN 1987A polarimetry is given that covers the period from day 2 to day 262. The catalog includes broad-band and narrow-band polarimetry and spectropolarimetry. The polarimetry has been corrected for the interstellar polarization along the line of sight to SN 1987A. Since the interstellar polarization is of the same order as the SN 1987A polarization, a correction for the interstellar polarization is essential for observing the intrinsic behavior of the SN 1987A polarization. It is hoped that the catalog will aid and encourage further analyses of the SN 1987A polarimetric data
45 citations
TL;DR: In this article, the power spectrum of surface microtopography is derived by solution of the small perturbation model for multiple incidence angle and multiple frequency radar data, and the results are close to those from measured micro-topography profiles.
Abstract: During the summer of 1988 an intensive field experiment was conducted in the vicinity of Pisgah lava field in the Mojave Desert. As part of the experiment, physical properties such as microtopography, composition, soil moisture, and dielectric constant at five different sites representing surfaces with rms heights varying from less than one centimeter to tens of centimeters were measured. In addition, polarimetric radar images at P-band, L-band and C-band were acquired at three different incidence angles with the NASA/JPL airborne imaging radar polarimeter. Using trihedral corner reflectors deployed in the area prior to imaging, the radar images were calibrated to provide values for each resolution element in each scene. This paper reports on the derivation of the power spectrum of surface microtopography by solution of the small perturbation model for multiple incidence angle and multiple frequency radar data. Power-law fits to the power spectra have exponents that are nearly the same for all surfaces. These values are close to those from measured microtopography profiles.
TL;DR: In this paper, the authors used laser-induced fluorescence to measure the concentration of mercury atoms in a Hg-Ar mixture in the vicinity of hot specimens, and the precision of temperature measurements based on the ideal gas law is + or - 2.6 percent at 1500-2000 K.
TL;DR: The validity of the 2*2 receive R and transmit T model for radar polarimeter systems, first proposed by H. Zebker et al. (1987), is questioned and is found to be invalid for many practical realizations of radar polarimeters.
Abstract: The validity of the 2*2 receive R and transmit T model for radar polarimeter systems, first proposed by H Zebker et al (1987), is questioned The model is found to be invalid for many practical realizations of radar polarimeters, which can lead to significant errors in the calibration of polarimetric radar images A more general model is put forward, which addresses the system defects which cause the 2*2 model to break down By measuring one simple parameter from a polarimetric active radar calibration (PARC), it is possible to transform the scattering matrix measurements made by a radar polarimeter to a format compatible with a 2*2 R and T matrix model Alternatively, the PARC can be used to verify the validity of the 2*2 model for any polarimetric radar system Recommendations for the use of PARCs in polarimetric calibration and to measure the orientation angle of the horizontal (H) and vertical (V) coordinate system are also presented >
TL;DR: In this paper, the concept of the polarimetric scattering matrix applicable to hydrometeors is reviewed to indicate the total number of measurands that is possible from a radar system with two orthogonal linear polarizations.
Abstract: The concept of the polarimetric scattering matrix applicable to hydrometeors is reviewed to indicate the total number of measurands that is possible from a radar system with two orthogonal linear polarizations. It is shown how to obtain this complete set of polarimetric measurands together with Doppler spectral moments through a single receiver by proper choice of polarization in a transmit-receive sequence pair.
TL;DR: In this paper, the Stokes Reflection Matrices (SVM) and the Kronecker expansion matrix (KEM) were used to obtain the optimal energy densities and powers for the one-and two-antenna cases.
Abstract: A problem originating in radar polarimetry is considered for which the radar target is to be characterized by its 4x4 Mueller matrix [M] properties in terms of a partially polarized wave treatment for the monostatic reciprocal and non-reciprocal cases. In order to compare our results with previous coherent treatments of optimizing the corresponding 2x2 Sinclair matrix [S], first the vector formalism for the coherent case is introduced. The coherent formulation is then extended via the coherency matrix (vector) approach to the partially polarized case with the aid of the Kronecker expansion matrix and the Stokes vector formulism. Distinction of the Stokes Reflection Matrices is made between the one-antenna and the two-antenna cases. For the one-antenna case, the reception of the optimal energy densities and powers is accomplished separately for the co-polarized and the cross-polarized channels which is a natural approach in radar polarimetry. For the two-antenna case, the reception of the optimal power is accomplished by adjusting the polarization state of the receiving antenna to match or mismatch the polarization state of the scattered wave. The “degen- erate Mueller matrix case” for purely coherent wave reception is analyzed first to facilitate comparison with previous methods of optimizing the corresponding Sinclair matrix [S]. Here, the Lagrangian multiplier method is used for determining the characteristic optimal polarization states subject to the constraint that the incident wave is purely polarized.
03 Jun 1991
TL;DR: A quasi-distributed optical fiber sensor that locates the positions of sensing units along a high-birefringence fiber by using white-light interferometry and measures the physical parameters by directly detecting the measured-induced cross coupling between two polarization modes is investigated.
Abstract: We investigate a quasi-distributed optical fiber sensor that locates the positions of sensing units along a high-birefringence fiber by using white-light interferometry and measures the physical parameters by directly detecting the measured-induced cross coupling between two polarization modes. Important factors that affect the performance of the system, such as cross-term spurious signals and thermostability, are analyzed. Preliminary experimental results of such a system with 10 pressure sensors are presented.
TL;DR: The linear polarization and intensity of a 22 degrees halo has been measured simultaneously at seven wavelengths as a function of scattering angle and the polarization pattern is found to be dominated by a narrow peak centered at the halo angle.
Abstract: The linear polarization and intensity of a 22° halo has been measured simultaneously at seven wavelengths as of scattering angle. The polarization pattern is found to be dominated by a narrow peak centered a function halo angle. The amount of polarization in this peak is much higher than expected from Fresnel at the alone. The observations are explained with a birefringence–diffraction halo polarization model. refraction of the hexagonal face of the halo-generating crystals is found to be 41 and 54 μm for two The effective diameter separate scans. An independent single-wavelength parhelion observation indicates a stronger birefringence in an even smaller angular scattering range and a crystal diameter of 220 μm. Crystal sizes peak concentrated derived from the halo intensity distributions are found to be consistent with those obtained from polarization. The data demonstrate the power of halo polarimetry as a tool for detection and identification of birefringent crystals in terrestrial or extraterrestrial atmospheres.
26 Mar 1991
TL;DR: In this article, a novel decomposition of the scattering matrix is presented with special reference to high-resolution imaging by decomposing the matrix into three different components, which allows for a better resolution of the target scattering properties as well as a better characterization of the type of scattering for the individual contributions.
Abstract: The basic theory of polarimetric radar and various decomposition theories are briefly reviewed A novel decomposition of the scattering matrix is then presented with special reference to high-resolution imaging By decomposing the scattering matrix into three different components, it is possible to resolve different types of scatterers even if they are within the same resolution cell of the image This allows for a better resolution of the target scattering properties as well as a better characterization of the type of scattering for the individual contributions The usefulness of this decomposition and the advantage in general of utilizing full polarimetric data in connection with radar target imaging are demonstrated by applying the decomposition to simulated images of a complex target model composed of a number of individual scatterers The extra information contained in the full polarimetric data as compared with single polarization data should greatly improve the possibility of noncooperative target recognition by radar >
01 Feb 1991
TL;DR: In this paper, a 50 cm-diam prototype of a novel Compton-scattering-type polarimeter for hard X-rays in the energy range 30-100 keV was described.
Abstract: The paper describes a 50-cm-diam prototype of a novel Compton-scattering-type polarimeter for hard X-rays in the energy range 30-100 keV. The characteristics of the prototype polarimeter were investigated for various conditions. It was found that, with polarized X-rays from a simple polarizer, the detection efficiency and the modulation factor of the polarimeter with a 40-mm thick scatterer were 3.2 percent and 0.57 percent, respectively, at about 60 keV.
TL;DR: In this article, a polarimeter was constructed that modulates the polarization state of a light wave at the frequencies ν 1 and ν 2, depending on the property searched for.
Abstract: A polarimeter was constructed that modulates the polarization state of a light wave at the frequencies ν1 and ν2. Depending on the property searched for, the frequencies of recorded intensity signals can be selected between ν1, ν2, 2ν1, 2ν2, ν1 ± ν2, and 2(ν1 ± ν2). Optical transfer functions are calculated by use of Jones matrices and experiments are simulated by numerical methods in order to analyze complex problems in polarization optics including propagation of error parameters. Measuring the azimuth and the ellipticity of a light wave with a dynamical analyzer the polarimeter serves for determining the linear and circular anisotropy of a crystal. A sensitivity of 2 × 10−7 radians is demonstrated. Application of the polarimeter is illustrated by measuring the gyration coefficient g11 of α quartz in two different ways. Furthermore, the polarimeter can be used for the measurement of linear and nonlinear electro‐optical and piezo‐optical effects between 20 and 800 K by subjecting the sample to periodical...
TL;DR: In this paper, the results from FP are compared with the results obtained by conventional methods of data analysis for the central safety factor of q 0 = 0.8 ± 0.1, which is in accordance with previous calculations.
Abstract: Function parametrization (FP) provides a way to perform complex data analysis in a fast and reliable manner that allows inter-shot analysis. The method has been used to analyse polarimetry and interferometry data in TEXTOR with the purpose of obtaining spatial distributions of the electron density and the toroidal plasma current. A standard TEXTOR discharge is investigated and the results from FP are compared with results obtained by conventional methods of data analysis. Agreement between the two methods is generally good. For the central safety factor the value of q0 = 0.8 ± 0.1 is in accordance with previous calculations. The new method can easily be modified to incorporate additional data.
TL;DR: Although the simulation possibilities are restricted due to the simplifying assumptions, the results are sufficiently realistic to allow for the study of the detectability of a particular man-made target in a SAR environment.
Abstract: A technique of synthetic aperture radar (SAR) image simulation is proposed. The method is based upon embedding of simulated man-made targets in a real background taken among the scenes captured by a spaceborne SAR. Scenes observed at 30 and 3 cm wavelength are used and the target dimensions are large enough with respect to the wavelength in order to compute the radar cross section from high frequency approximation techniques. Once the simulated image of the target is computed, the embedding process is performed bearing in mind the problems involved with this particular process. Although the simulation possibilities are restricted due to the simplifying assumptions, the results are sufficiently realistic to allow for the study of the detectability of a particular man-made target in a SAR environment. >
Journal Article•
TL;DR: In this article, optical data from polarimetry, photometry and astrometry are presented for the jet of 3C 273, which confirm the high degree of polarization at the outer end of the jet as well as the drop in polarization level in the inner region.
Abstract: New optical data from polarimetry, photometry and astrometry are presented for the jet of 3C 273. They confirm the high degree of polarization at the outer end of the jet as well as the drop in polarization level in the inner region. The optical hot spot counterpart at the outer extreme of the jet reveals itself by a 90° flip in polarization angle very similar to that found in the radio data.
TL;DR: In this article, a three-dimensional position sensitive imaging detector has been proposed for the prospective ESA/NASA gamma-ray satellite, INTEGRAL, based on two layers of bar shaped CsI(T1) crystals viewed by photodiodes.
Abstract: A three-dimensional position sensitive imaging detector has been proposed for the prospective ESA/NASA gamma-ray satellite, INTEGRAL. The instrument is based on two layers of bar shaped CsI(T1) crystals viewed by photodiodes. The GEANT3 Monte Carlo simulation package has been used to assess the spectroscopic and enhanced imaging performance of this detector and an original routine has been written to assess its capabilities as a Compton polarimeter. A description of the algorithm of this routine is given with the results of both GEANT3 and the polarization simulations.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
03 Jun 1991
01 Jan 1991
TL;DR: In this article, a multichannel solar magnetic field telescope was used for magnetic and velocity measurements in IZMIRAN, and a two-dimensional polarimeter with CCD image sensors and piezo-elastic modulators was used.
Abstract: : Partial contents include: (1) Ultraviolet polarimetry with UVSP; (2) Progress on the analysis of BBSO vector magnetograms; (3) Solar instruments for magnetic and velocity measurements in IZMIRAN; (4) Solar vector magnetic field measurements; (5) Vector magnetography; (6) A brief introduction to the multichannel solar magnetic field telescope; (7) Two-dimensional polarimeter with CCD image sensors and piezo-elastic modulators; (8) High spatial resolution polarimetry using filtergrams; (9) Systemic errors in polarimeter calibration due to imperfect calibration optics; (10) Using the Zeeman spectral-polarization symmetry for telescope calibration; (11) Polarization of the domeless solar telescope of the Hida Observations; (12) Stokes profile analysis of a sunspot using the MSFC magnetograph; (13) High spatial resolution observations of magnetic flux elements; (14) Observation and interpretation of H alpha polarization in solar flares; (15) Currents and flares in a highly nonpotential active region; (16) Properties of the white-light corona polarization during maximum of the solar cycle; (17) Broadband linear polarization: the Sun and the F-G-K Stars; (18) Polarimetry in the IR; (19) Direct inference of the field vector from stokes profiles; and (20) Polarimetric studies of solar magneto- sensitive spectral lines