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Hybrid Meeting "2nd GNSS Polarimetric Radio Occultations User Workshop" What: Over 80 people from 14 countries, 3 continents, and over 40 different affiliations, from government agencies, research centers, universities, and the commercial space sector, discussed the status of the polarimetric radio occultation technique and applications being developed from the current and future observations, with focus on its use for and in numerical weather prediction modeling. When: 28-29 November 2023 Where: Hybrid, at the Keck Center, California Institute of Technology, Pasadena, California. Co-organized by JPL and ICE-CSIC/IEEC. KEYWORDS: Atmosphere; Cloud microphysics; Convective-scale processes; Thermodynamics; Numerical weather prediction/ forecasting; Convective parameterization, 1. Introduction Conventional radio occultations (ROs) track the phase delay induced by water vapor and air density gradients in Global Navigation Satellite System (GNSS) signals as they propagate through Earth's [...]

Detecting and quantifying chirality is important in fields ranging from analytical and biological chemistry to pharmacology (1) and fundamental physics (2): it can aid drug design and synthesis, contribute to protein structure determination, and help detect parity violation of the weak force. Recent developments employ microwaves (3), femto-second pulses (4), superchiral light (5) or photoionization (6) to determine chirality, yet the most widely used methods remain the traditional methods of measuring circular dichroism and optical rotation. However, these signals are typically very weak against larger time-dependent backgrounds (7). Cavity-enhanced optical methods can be used to amplify weak signals by passing them repeatedly through an optical cavity, and two-mirror cavities achieving up to [10.sup.5] cavity passes have enabled absorption and birefringence measurements with record sensitivities (8-10). But chiral signals cancel when passing back and forth through a cavity, while the ubiquitous spurious linear birefringence background is enhanced. Even when intracavity optics overcome these problems (11-15), absolute chirality measurements remain difficult and sometimes impossible. Here we use a pulsed-laser bowtie cavity ringdown polarimeter with counter-propagating beams (16,17) to enhance chiral signals by a factor equal to the number of cavity passes (typically > [10.sup.3]); to suppress the effects of linear birefringence by means of a large induced intracavity Faraday rotation; and to effect rapid signal reversals by reversing the Faraday rotation and subtracting signals from the counter-propagating beams. These features allow absolute chiral signal measurements in environments where background subtraction is not feasible: we determine optical rotation from α-pinene vapour in open air, and from maltodextrin and fructose solutions in the evanescent wave produced by total internal reflection at a prism surface. The limits of the present polarimeter, when using a continuous-wave laser locked to a stable, high-finesse cavity, should match the sensitivity of linear birefringence measurements (8) (3 x [10.sup.-13] radians), which is several orders of magnitude more sensitive than current chiral detection limits (7,14,15) and is expected to transform chiral sensing in many fields., Our approach to the absolute measurement of chirality makes use of the development of a polarimeter based on a bowtie ring cavity, as proposed recently (16,17). Unlike a two-mirror cavity, [...]

Information about the three-dimensional structure of solar magnetic fields is encoded in the polarized spectra of solar radiation by a host of physical processes. To extract this information, solar spectra must be obtained in a variety of magnetically sensitive spectral lines at high spatial, spectral, and temporal resolution with high precision. The need to observe many different spectral lines drives the development of Stokes polarimeters with a high degree of wavelength diversity. We present a new paradigm for the design of polarization modulators that operate over a wide wavelength range with near-optimal polarimetric efficiency and are directly applicable to the next generation of multiline Stokes polarimeters. These modulators are not achromatic in the usual sense because their polarimetric properties vary with wavelength, but they do so in an optimal way. Thus, we refer to these modulators as polychromatic. We present here the theory behind polychromatic modulators, illustrate the concept with design examples, and present the performance properties of a prototype polychromatic modulator. OCIS codes: 000.2170, 120.5410, 230.4110, 230.5440, 260.5430, 350.1260.

We use a laser high-harmonics-based extreme-ultraviolet (EUV) polarimeter to determine the optical constants of elemental uranium in the wavelength range from 10 to 47 nm. The constants are extracted from the measured ratio of p-polarized to s-polarized reflectance from a thin uranium film deposited in situ. The film thickness is inferred from a spectroscopic ellipsometry measurement of the sample after complete oxidation in room air. Uranium has been used as a high-reflectance material in the EUV. However, difficulties with oxidation prevented its careful characterization previous to this study. We find that measured optical constants for uranium vary significantly from previous estimates. [c] 2010 Optical Society of America OCIS codes: 160.3900, 160.4760, 120.4530, 120.5410, 310.6860, 340.7480.

We present a polarimetric instrument suitable for the simultaneous measurement of angle resolved normalized Mueller matrices for polar angles ranging from 0[degrees] to 60[degrees] and all azimuths. The polarimetric modulation and analysis are performed by means of an optimized polarization state generator and analyzer based on nematic liquid crystals. A high numerical aperture (0.95) microscope objective is used in double pass to illuminate the sample, with its rear focal plane imaged on a low noise CCD. This polarimeter can be used either in reflection, with the sample set in the objective front focal plane, or in transmission, for thin transparent samples. This latter configuration, which involves an additional spherical mirror with its center of curvature at the objective front focus, is described in detail. This instrument was used to accurately determine the directions of the optic axes and the angular dependence of the retardation of a biaxial polyethylene terephthalate (PET) plastic substrate in spite of the strong depolarization essentially due to the source 10 nm spectral width or the limitation in angular resolution due to the pixels distribution of the CCD combined with the sample large retardation. OCIS codes: 120.2130, 120.5410.

We optimize a general class of complete multispectral polarimeters with respect to signal-to-noise ratio, stability against alignment errors, and the minimization of errors regarding a given set of polarization states. The class of polarimeters that are dealt with consists of at least four polarization optics each with a multispectral detector. A polarization optic is made of an azimuthal oriented wave plate and a polarizing filter. A general, but not unique, analytic solution that minimizes signal-to-noise ratio is introduced for a polarimeter that incorporates four simultaneous measurements with four independent optics. The optics consist of four sufficient wave plates, where at least one is a quarter-wave plate. The solution is stable with respect to the retardance of the quarter-wave plate; therefore, it can be applied to real-world cases where the retardance deviates from [lambda]/4. The solution is a set of seven rotational parameters that depends on the given retardances of the wave plates. It can be applied to a broad range of real world cases. A numerical method for the optimization of arbitrary polarimeters of the type discussed is also presented and applied for two cases. First, the class of polarimeters that were analytically dealt with are further optimized with respect to stability and error performance with respect to linear polarized states. Then a multispectral case for a polarimeter that consists of four optics with real achromatic wave plates is presented. This case was used as the theoretical background for the development of the Airborne Multi-Spectral Sunphoto- and Polarimeter (AMSSP), which is an instrument for the German research aircraft HALO. OCIS codes: 120.0120, 120.0280, 120.5410, 220.0220, 220.4830.

This paper presents a case study of C-band backscatter observations of snow during a Chinook event. A surface-based C-band polarimetric data set collected in February 2006 is used to contrast the polarimetric response to sampled conditions of bare frozen ground, cold snow-covered ground, and snow during a Chinook event. Chinook activity is inherently spatially and temporally variable across the region in winter and produces considerable spatial variability of snow-cover physical properties associated with snow--water-equivalent (SWE) estimates. A temporal analysis of polarimetric backscatter sensed during a Chinook-induced ablation event on February 27, 2006 is used to describe the associated changes in snow conditions and scattering mechanisms. Analysis reveals that the polarimetric surface-based C-band scatterometer data respond to changes in snow parameters associated with the specific ground and snow conditions and to the temporal Chinook ablation event. Use of the copolarizations, cross-polarization, depolarization ratio, copolarization ratio, complex copolarization correlation coefficient, and the copolarized phase difference information show promise in describing changes in snow physical parameters, differing ground and snow conditions, and transitional ablation events, based on differing scattering mechanisms. This paper infers that an increase in volume scattering and fluctuations in surface scattering during the Chinook ablation event may be associated with specific physical changes such as density, crystal structure, and permittivity caused by wind speed. This paper has implications for remotely sensed estimations of snow-covered area (SCA) and SWE. Association of SCA and SWE with backscatter coefficients is not explicit in this paper; however, changes in SWE and snow properties are inferentially linked to changes in backscatter. Index Terms--Chinook, radar polarimetry, radar scattering, snow ablation, snow-covered area (SCA), snow--water equivalent (SWE).

Backscatter signatures of multiyear sea ice (MYI) during the late summer and early fall season before the fall freeze-up in the Canadian Arctic Archipelago (CAA) have been obtained through the use of a ship-based polarimetric scatterometer. The device operates in C-band, and measurements were conducted in swaths from incidence angles of 20[degrees]-60[degrees]. Three characteristic sites on MYI floes were investigated in the high Arctic and the central Arctic regions. In situ snow and sea-ice thermophysical data were collected at each site in conjunction with local scatterometer measurements. The thermophysical data were subsequently analyzed using dielectric modeling techniques and coupled with the backscattering measurements ([sigma][degrees]). Observed backscatter values and ratios were found to be in agreement with literature data, with volumetric scattering as the dominant scattering mechanism. Index Terms--Canadian Arctic, multiyear sea ice (MYI), polarimetric radar, remote sensing, snow.

Here we experimentally demonstrate measurements of the wavelength-dependent phase response of a surface plasmon resonance sensor using a spectral interferometric technique. By using a broadband incoherent fiber light source and a polarimetry configuration with a high-birefringence component, the spectral phase response of a surface plasmon resonance sensor can be retrieved. A combination of wavelength interrogation and phase detection is enabled by our proposed scheme. In contrast to the previously demonstrated heterodyne or spatial fringe detection schemes, this in-line optical configuration is much simpler and can be very compact when implemented with advanced fiber optic and integrated components. OCIS codes: 240.6680, 280.4788, 120.5050, 120.2130.

In this paper, effects of birefringence on radio waves obliquely propagating though polar ice sheets are examined to facilitate interpretations of bistatic and side-looking radar data. A formalism applicable for arbitrary radar configurations is developed to predict the returned power from within and beneath the ice sheets that have arbitrary alignments of ice crystals (ice fabrics). We applied this formalism to a range of ice fabrics found in ice cores and assessed the effects of birefringence in terms of ray-path configurations, ice fabrics, and radar frequency. Predicted frequency dependence of the bed return power replicates prominent features observed at Greenland NGRIP ice-core site. Results show that birefringence in ice of 1 km or more thickness with strong (weak) fabric can reduce the power returned from the bed 2 dB or more at frequencies higher than 200 MHz (20 MHz) as compared to isotropic ice. This suggests that quantitative interpretation of the power returned from the bed requires careful assessment of birefringence almost everywhere over the ice sheets. Application of this formalism also suggests a radar-frequency range usable for attenuation measurements, possible effects of fabric on synthetic aperture radar processing, and a feasibility of remote sensing of ice fabric. Index Terms--Arctic regions, birefringence, ice, radar polarimetry.

A polarization imaging spectrometer based on a modified Savart polariscope with a moving wedge prism is presented. The principle of the instrument is described, and the optical path difference as a function of the moving wedge prism's moving displacement is calculated and analyzed. It employs a common-path configuration and is not sensitive to the nonuniform variation of moving speed and environmental vibrations. In comparison with the polarization imaging spectrometer based on the Savart polariscope, this spectrometer is a framing instrument rather than a pushbrooming device. Only the transmission of birefringent materials and detector sensitivity limit the available spectral range of such an instrument. OCIS codes: 120.6200, 300.6190, 260.1440, 260.5430.

A spectro-polarimetric method is presented to allow the recovery of the frequency dependent polarization modulation function for an achromatic half-wave plate. We show how the non ideal nature of the modulator can be characterized for removal of both instrument effects and variations related to the source spectral index. OCIS codes: 120.5410, 230.4110.

Pathological changes of skin will change the tissue's birefringence and structure, which can be measured by the polarization and spectral changes of the tissue's scattering light. Light-scattering spectropolarimetry is an effective tool to measure these features for quantitative pathology analysis. An epithelial tissue imaging spectropolarimeter is proposed to acquire the spectral, polarimetric, and spatial characteristic changes of the tissue, and then a spectropolarimetric correction method is proposed to compute the tissue's polarimetric spectrum, which can be used for pathological analysis of tissue. Finally, to aid doctors for more accurate clinical diagnosis, a false color mapping based spectropolarimetric image fusion method is proposed to enhance the visual differences between normal skin and pathological skin. Experimental results demonstrate the potential of the proposed techniques for pathological diagnosis and treatment evaluation of skin. OCIS codes: 170.6510, 260.5430, 100.2980, 100.5010.

The coastal zones of the Korean peninsula are well known for their large tide ranges and vast expanse of intertidal flats. In this paper, methods of extracting the roughness of the scattering surface of intertidal mudflats from polarimetric synthetic aperture radar (SAR) data have been investigated. The L-band NASA/Jet Propulsion Laboratories airborne SAR data, which were acquired in the intertidal zone during PACRIM-II Korea campaign, were used to estimate the roughness of intertidal mudflats. Surface roughness can be utilized as a useful parameter to monitor the fishery activities in intertidal flats as well as the changes in textural characteristics of surface sediments. In order to retrieve roughness parameters, such as the rms height and the Correlation length, of intertidal mudflats, three types of roughness inversion algorithms, based on the Integral Equation Method (IEM), semiempirical, and extended-Bragg models, have been investigated and developed. The inversion algorithms based on the IEM and semiempirical models can be applied to the dual-polarized SAR, while the extended-Bragg model-based inversion approach is also applicable to the fully polarimetric SAR observations. Results indicate the fully polarimetric approach is more pertinent to monitor geophysical parameters from space than the dual polarimetric approach, even if it is possible to reduce the number of unknown surface variables in the specific case of inversion problems. Index Terms--Intertidal flat, surface roughness, surface scattering model, synthetic aperture radar (SAR) polarimetry.

Linear (spectro) polarimetry is usually performed using separate photon flux measurements after spatial or temporal polarization modulation. Such classical polarimeters are limited in sensitivity and accuracy by systematic effects and noise. We describe a spectral modulation principle that is based on encoding the full linear polarization properties of light in its spectrum. Such spectral modulation is obtained with an optical train of an achromatic quarter-wave retarder, an athermal multiple-order retarder, and a polarizer. The emergent spectral modulation is sinusoidal with its amplitude scaling with the degree of linear polarization and its phase scaling with the angle of linear polarization. The large advantage of this passive setup is that all polarization information is, in principle, contained in a single spectral measurement, thereby eliminating all differential effects that potentially create spurious polarization signals. Since the polarization properties are obtained through curve fitting, the susceptibility to noise is relatively low. We provide general design options for a spectral modulator and describe the design of a prototype modulator. Currently, the setup in combination with a dedicated retrieval algorithm can be used to measure linear polarization signals with a relative accuracy of 5%. OCIS codes: 120.0280, 120.5410, 120.6200, 120.6780, 160.1190, 260.5430.

Systematic errors specific to a snapshot Mueller matrix polarimeter are studied. Their origins and effects are highlighted, and solutions for correction and stabilization are proposed. The different effects induced by them are evidenced by experimental results acquired with a given setup and theoretical simulations carried out for more general cases. We distinguish the errors linked to some imperfection of elements in the experimental setup from those linked to the sample under study. OCIS codes: 230.5440, 260.5430.

This paper addresses the potential and limitations of polarimetric synthetic aperture radar (SAR) interferometry (Pol-InSAR) inversion techniques for quantitative forest-parameter estimation in tropical forests by making use of the unique data set acquired in the frame of the second Indonesian Airborne Radar Experiment (INDREX-II) campaign--including Pol-InSAR, light detection and ranging (LIDAR), and ground measurements--over typical Southeast Asia forest formations. The performance of Pol-InSAR inversion is not only assessed primarily at L- and P-band but also at higher frequencies, namely, X-band. Critical performance parameters such as the 'visibility of the ground' at L- and P-band as well as temporal decorrelation in shorttime repeat-pass interferometry are discussed and quantitatively assessed. Inversion performance is validated against LIDAR and ground measurements over different test sites. Index Terms--Forest height, polarimetric SAR interferometry (Pol-InSAR), synthetic aperture radar (SAR), temporal decorrelation, tropical forest.

This paper compares two well-known polarimetric decomposition theorems, Cloude-Pottier and Freeman-Durden, applied to L- and C-band Airborne Polarimetric Synthetic Aperture Radar (AIRSAR-POLSAR) data acquired during the ColdLand Processes Field Experiments. Three field campaigns were carried out in February 2002, March 2002, and March 2003 over a snow-covered open terrain, a sparse coniferous forest, and a dense coniferous forest. The analysis evaluates the ability of the two target decomposition methods for the identification and understanding of the main scattering mechanisms. Index Terms--Cold-Land Processes Field Experiments (CLPX), forested areas, polarimetry, scattering mechanisms, snow, target decomposition (TD).

In this paper, the potential of using polarimetric SAR (PolSAR) acquisitions for the estimation of volumetric soil moisture under agricultural vegetation is investigated. Soil-moisture estimation by means of SAR is a topic that is intensively investigated but yet not solved satisfactorily. The key problem is the presence of vegetation cover which biases soil-moisture estimates. In this paper, we discuss the problem of soil-moisture estimation in the presence of agricultural vegetation by means of L-band PolSAR images. SAR polarimetry allows the decomposition of the scattering signature into canonical scattering components and their quantification. We discuss simple canonical models for surface, dihedral, and vegetation scattering and use them to model and interpret scattering processes. The performance and modifications of the individual scattering components are discussed. The obtained surface and dihedral components are then used to retrieve surface soil moisture. The investigations cover, for the first time, the whole vegetation-growing period for three crop types using SAR data and ground measurements acquired in the frame of the AgriSAR campaign. Index Terms--Model-based decomposition, polarimetric SAR (PolSAR), scattering mechanisms, surface-soil-moisture estimation.

The Mueller matrix imaging method is a powerful tool for target detection. In this study, the effect of the air-sea interface on the detection of underwater objects is studied. A backward Monte Carlo code has been developed to study this effect. The main result is that the reflection of the diffuse sky light by the interface reduces the Mueller image contrast. If the air-sea interface is ruffled by wind, the distinction between different regions of the underwater target is smoothed out. The effect of the finite size of an active light source is also studied. The image contrast is found to be relatively insensitive to the size of the light source. The volume scattering function plays an important role on the underwater object detection. Generally, a smaller asymmetry parameter decreases the contrast of the polarimetry images. OCIS codes: 010.4450, 120.5410, 290.1350, 290.7050, 030.5620.

We present a detailed analysis of the airborne passive microwave remote-sensing data that were collected at a broad range of microwave bands and at a high spatial resolution during the 2002 and 2003 National Aeronautics and Space Administration Cold Land Processes Experiment (CLPX). An accurate measurement of snowpack properties using passive microwave observations requires the detailed knowledge of the relationship between snowpack geophysical parameters and the upwelling polarimetric brightness signature. The principle microwave instrument used for the CLPX was the polarimetric scanning radiometer (PSR), which provided ~100-m resolution maps of the snow emissivity at all Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) bands during several intensive observation periods over the Colorado Rocky Mountains. The observed conditions included drought, normal snowpack, and spring snowmelt. The PSR and related ground-based observations of snowpack properties made during the 2002 and 2003 CLPX campaigns provide a comprehensive high-resolution passive microwave data set. Results show that the high-resolution PSR data exhibit emissivity modes that are similar to those observed in the historical data sets, and that the empirical relationships between the emissivity and the snow water equivalent (SWE), after the effects of macrovegetation are removed, closely match those found in the past theoretical studies. The use of the 89-GHz channel in the empirical relationships provides improved accuracy under dry snow conditions and a small SWE; however, the variability of the SWE--emissivity relationships increases with an increasing SWE. A summary of the observed relationships between the emissivity spectra of snow and snowpack properties is presented. Comparison of the total water content from the AMSR-E and PSR observations shows that the satellite measurements underestimated the total volume of water storage from airborne observations on the average by a factor of five. Index Terms--Airborne polarimetric scanning radiometer (PSR), beam polarization correction, georegistration, microwave emissivity, passive microwave remote sensing, retrieval algorithm development, snowpack, snow water equivalent (SWE), topography, validation.

The influence of surface roughness on the polarimetric performance of a wire-grid polarizer (WGP) is numerically investigated using rigorous coupled-wave analysis over 100 random surface realizations. Surface roughness is modeled with a Gaussian surface, represented by two independent parameters: surface height deviation and correlation length of a profile. The results show that WGP performance can suffer from significant degradation as well as increased deviation with surface roughness, although the extent varies with specific parameters. The influence of roughness was also examined with respect to grating period as a WGP parameter and incident light properties, such as wavelength and angle. OCIS codes: 050.1950, 120.5410, 230.5440, 240.5770, 260.5430.

Retinal images of approximately 1[degrees] of visual field were recorded with a homemade scanning laser ophthalmoscope. The benefit of using a nonlinear registration technique to improve the summation process when averaging frames, rather than a standard approach based on correlation, was assessed. Results suggest that nonlinear methods can surpass linear transformations, allowing improved contrast and more uniform image quality. The importance of this is also demonstrated with specific polarization measurements to determine the degree of polarization across an imaged retinal area. In such a context, where this parameter of polarization is extracted from a combination of registered images, the benefit of the nonlinear method is further increased. OCIS codes: 100.2000, 100.2980, 110.5405, 170.5755, 330.7327.

In spaceborne synthetic aperture radar (SAR), a single-polarization on-transmit offers twice the swath width compared to full polarization. This is linked to SAR system design issues, and, without getting into the technical details deserving by themselves a full paper, we can just mention the swath characteristics of ALOS PALSAR (the Advanced Land Observing Satellite, Phased Array L-Band Synthetic Aperture Radar), reducing from 70 km for the dual-pol mode to 30 km for the full polarization mode. The reduced coverage in the full polarization mode has a harmful impact on the revisit time, which is always a major drive for the Earth-observing community. The options chosen up to now for dual-pol system designs (or single-polarization on-transmit) rely on a linear polarization on-transmit [either horizontal (H) or vertical (V)], with two orthogonal polarizations on-receive. Souyris and Raney in earlier papers proposed more pertinent alternatives for the selection of the transmit polarization leading to a better characterization of the scattering mechanisms. In this paper, the analysis is pursued in more depth by including the effect of the ionosphere on the wave propagation and extending the applications to polarimetric interferometry SAR (PolInSAR). A compact mode is developed where the transmit polarization is circular, whereas the only constraint on the two receiving polarizations is independence. Indeed, the choice of the polarizations of the two receive channels does not matter, as any polarization on-receive can be synthesized from these two measurements. This is, however, not the case for the unique transmit polarization. At a low frequency, where the ionosphere has a significant effect, the circular transmit polarization is the only sensible option, as it provides an effective constant polarization as seen by the scattering surface. This is an essential condition for a meaningful multitemporal analysis. Both the polarimetric SAR applications and the PolInSAR applications in the context of this compact polarimetry (CP) mode are explored. A pseudocovariance matrix can be reconstructed following Souyris' proposed approach for distributed targets and is shown to be very similar to the full polarimetric (FP) covariance matrix. The reconstruction of the cross-polarized Sigma0 is shown to be reliable and to have very low sensitivity to Faraday rotation. A PolInSAR vegetation height inversion for P-band is presented and applied to the CP data with a level of performance that is similar to the one derived from FP (a 1.2-m root-mean-square height error on the ONERA Airborne radar (RAMSES) data over the Landes Forest). A procedure is developed to correct for the ionospheric effects for the PolInSAR acquisition in the FP or CP mode and is assessed on the data simulated from an airborne acquisition. The results demonstrate that the technique is efficient and robust. The calibration of CP data is identified as an important challenge to be solved, and some clues are provided to address the problem. Index Terms--Compact polarimetry (CP), forest height inversion, low frequency, polarimetric interferometry, polarimetry, synthetic aperture radar (SAR).

In the past few years, imaging spectroscopy has been widely used. However, it only acquires intensity information in a narrow electromagnetic band, ignoring the polarimetric information of the electromagnetic wave and resulting in inaccurate object detection. According to electromagnetic theory, the reflected spectral signature depends on the elemental composition of objects residing within the scene, and the radiation's polarization characteristic is sensitive to surface features, such as relative smoothness and conductance. Independently, spectral and polarimetric features give incomplete representations of an object of interest. These representations are complementary, and it is expected that the combination of complementary information will reduce false alarms, improve confidence in target identification, and improve the quality of the scene description. Imaging spectropolarimetric technology as a new sensing method can acquire polarimetric information at narrow electromagnetic bands, but there are a few results showing how to combine these complementary features to detect objects in clutter. In this paper, a spectropolarimetric projection scheme is proposed to divide the spectropolarimetric data set into two parts: 1) a polarimetric spectrum data set and 2) a polarimetric data cube. Then, the polarimetric spectrum anomaly feature extraction method is used to deal with the polarimetric spectrum data set, and the adaptive polarimetric information fusion method is proposed to extract the feature from the polarimetric data cube. Finally, these features are combined by the Choquet integral to achieve better detection performance. The algorithm is applied to one complex scene, and detailed detection performance is evaluated. Index Terms--Anomaly detection, fuzzy integral, imaging spectropolarimetry, information fusion, spectropolarimetric projection.

Recent research has demonstrated the value of polarimetric measurements for the correction of rain-path attenuation at X-band radar frequency and the estimation of rain parameters including drop-size distributions (DSD). The issue this paper is concerned with is to what degree uncertainties in attenuation correction can affect the estimation of DSD. Since attenuation-correction uncertainty enhances with rain path, our hypothesis is that DSD retrieval uncertainty at X-band may deteriorate with range. In this paper, we evaluate the relative accuracy of X-band DSD retrieval against DSD estimates from S-band radar observations and in situ disdrometer spectra. We present comparisons of various techniques for estimating DSD model parameters from attenuation-corrected X-band dual-polarization radar data. Coincident X-band polarimetric-radar (XPOL) and S-band polarimetric-radar dual-polarized radar measurements from the International [H.sub.2]O Project experiment as well as coincident XPOL (MP-X) measurements over disdrometer during a typhoon storm case in Japan are used to assess the accuracy of the different DSD retrieval algorithms applied to X-band radar measurements. Index Terms--Attenuation correction, drop-size distribution (DSD) retrievals, polarimetric radar, S-band radar, X-band radar.

In this paper, a new and improved L-band version of the correlated noise calibration standard (CNCS) has been developed to aid in the characterization of polarimetric microwave radiometers. The CNCS generates a series of known polarimetric test signals using a two-channel commercial arbitrary waveform generator (AWG) and a pair of frequency-upconversion modules. When it is inserted in place of the antenna used by a radiometer-under-test (RUT), it can fully characterize the polarimetric response of the receiver portion of the RUT. Both hardware and software improvements have been made over a previous version of the CNCS. The frequency upconverters now include integral warm and cold calibration-reference targets to automatically compensate for small drifts in AWG output-signal strength. The procedure used to calibrate the RUT has been generalized to correct for nonideal characteristics of the CNCS itself. Moreover, the effects on the derived polarimetric gain matrix of impedance mismatches between the RUT, and either the CNCS or the antenna have been determined. Details of the CNCS improvements are presented. The results of an experimental demonstration of its use and of a series of validation tests of its performance are also presented. Index Terms--Calibration, microwave radiometry, noise generators, polarimetry.

With the synthetic aperture radar (SAR) sensor PALSAR onboard the Advanced Land Observing Satellite, a new full-polarimetric spaceborne L-band SAR instrument has been launched into orbit. At L-band, Faraday rotation (FR) can reach significant values, degrading the quality of the received SAR data. One-way rotations exceeding 25[degrees] are likely to happen during the lifetime of PALSAR, which will significantly reduce the accuracy of geophysical parameter recovery if uncorrected. Therefore, the estimation and correction of FR effects is a prerequisite for data quality and continuity. In this paper, methods for estimating FR are presented and analyzed. The first unambiguous detection of FR in SAR data is presented. A set of real data examples indicates the quality and sensitivity of FR estimation from PALSAR data, allowing the measurement of FR with high precision in areas where such measurements were previously inaccessible. In examples, we present the detection of kilometer-scale ionospheric disturbances, a spatial scale that is not detectable by ground-based GPS measurements. An FR prediction method is presented and validated. Approaches to correct for the estimated FR effects are applied, and their effectiveness is tested on real data. Index Terms--Faraday rotation (FR) correction, FR estimation, ionospheric effects, L-band synthetic aperture radar (SAR).

Cloud studies were carried out with a polarimetric bistatic lidar setup at the Arctic Lidar Observatory for Middle Atmosphere Research in Andenes (69[degrees]N, 16[degrees]E), Norway. Measurements were performed at altitudes between 1.5 and 10.5 km, corresponding to scattering angles between 130[degrees] and 170[degrees]. The geometry, not restricted to the parallel or perpendicular laser polarization directions, gave a well-defined scattering angle, which together with polarization characterization, was used to investigate the scattering particles. The principles of the technique and the first results are presented together with an evaluation of the capabilities. OCIS codes: 010.0280, 010.1350, 010.1615, 010.2940, 280.3640, 280.1100.