We present progress towards an automated system that can segment tropical cyclones (TCs) and their neighboring regions from geostationary infrared brightness temperature images. The purpose of these segmentation maps is to provide an area that can be used to compute the contribution of TCs to the upwelling radiation budget. Our previous work has identified regions of TC clouds, but it is known that TCs impact a larger area than just those covered by their clouds. Hence it is necessary to properly label both the TC clouds and the associated clear-sky regions in the vicinity of the TCs. Here we present a convolutional neural network method that can be used to reproduce cloud masks generated with our earlier, first-principles algorithm. We also discuss our efforts to create an extended training set of TC masks that include both clouds and clear sky.

Analysis of data generated by Mueller matrix polarimeters using two photoelastic modulators has been evolving with the improvements in data acquisition and digital signal processing (DSP). Historical processing of the temporal data generated by these devices has involved isolating the frequencies via hardware signal processing (e.g., lock-in amplifiers) or the numerical computation of Fourier integrals of recorded temporal data. Both avenues have their advantages, but the DSP aspects of the latter provide greater flexibility in choice of harmonics for processing. While conventional processing uses one harmonic for each desired Mueller matrix element, recent work has demonstrated that theoretical improvements are possible by coherently combining the information in multiple harmonic channels for each element. We demonstrate some recent progress in DSP that enables these polarimeters' data to be more fully exploited by addressing two key issues in the Fourier domain: spectral leakage and phase recovery. Adequately addressing these issues enables numerical analysis of the temporal data in the complex Fourier domain and delivers Mueller matrix results in which spectral phase information is used to recover the matrix elements and determine their signs automatically. We explore the application of this complex analysis and how the precision and accuracy of the results are affected by common experimental and DSP limitations compared to the usual magnitude-only analysis in the Fourier domain. The multi-harmonic method can provide a theoretical factor of 1.3-1.7 improvement in instrumental precision, and our experimental results approach that theoretical range.

Multi-domain modulated polarimeters offer benefits such as an increased channel separation in the frequency domain, allowing a reduction in cross-talk and improving their performance in the retrieval of the polarization information. Although the experimental implementation of this kind of system cannot be realized with perfect, periodic modulation due to practical limitations, machine learning methods have been used to obtain the correct calibration parameters and reduce errors during the data reduction stage. The aforementioned strategies have improved the performance of modulated polarimeters. However, in the modulated polarimetric systems reported in the literature, the modulation parameters are set during the design stage and remain unchanged during operation. In this work, we present a dynamic, spatially channeled, imaging Mueller matrix polarimeter in which the modulation parameters of the polarization state generator (PSG) can be adjusted during operation to achieve better performance depending on the spatial frequency properties of the scene under analysis. We present experimental evidence of the feasibility of the method, discuss its capabilities and current limitations, and describe a strategy to retrieve the Mueller matrix of a scene.

We model a linear EZ antenna array for HPEM applications. Equivalent circuit models of the single element EZ antenna and two element array antenna are presented, relating antenna performance and field coupling to physical parameters. This fully parameterized circuit model can be used to load the transmission line or waveguide feed and design a particular aperture field configuration, which can then be synthesized through the physical model.

Traditionally, polarimetric imaging data is visualized by mapping angle of polarization, degree of polarization, and intensity to hue, saturation, and value coordinates of HSV color space.Due to possible perceptual uniformity issues in HSV, a method based on CAM02-UCS color space has been recently proposed.In this user study, the perceptual uniformity and nonlinear bias of the encoding of the degree of polarization parameter into the chromatic magnitude color channel is modeled by a power-law relationship between stimulus scale level and is estimated from responses to paired 2-alternative forced choice questions using Maximum Likelihood Difference Scaling.Estimated exponent and noise parameters for these methods are compared for same-hue and different-hue conditions to determine whether the chromatic magnitude channel can be used to orthogonality encode data parameters independently from the hue channel.Overall, the HSV condition displayed more nonuniformity, more nonlinear bias, and more non-orthogonality than the UCS condition.The results here indicate a lower bound for differences between methods since the intensity was chosen for the ''best case'' of HSV.These results further support the claim that the chromatic magnitude color channel of a uniform color space can be used to encode a data parameter independently of the hue channel in a multivariate colormapping visualization.

A polarimetric scatterometer was designed and constructed at UNSW-Canberra’s Advanced Sensing Laboratory to enable the production of spectrally-resolved material bi-directional reflectance distribution functions (BRDFs). The capability to characterise the polarization properties of light scattered from those materials yields a complete Mueller matrix from which a polarimetric BRDF (pBRDF) can be determined. In this study, the Mueller matrix of a triple junction solar cell sample was characterized to demonstrate the polarimetric measurement capabilities of the scatterometer as a function of wavelength.

Techniques similar to Poisson Image Editing are used to construct a grayscale image representing the phase angle of polarization which produces consistent, high-contrast images for enhanced visual analysis of data from polarization imaging.

Snapshot channeled polarimeters forgo temporal modulation in favor of modulating polarization information in either space or wavenumber. We have recently introduced methodologies for describing both channeled and partial polarimeters. In this paper, we focus on the nine-reconstructables design, which limits the resolution loss by reducing the number of carriers. The architecture offers a number of favorable trade-offs: a factor of 5.44 increase in spatial bandwidth or a factor of 3.67 increase in spectral bandwidth, for a smaller amount of temporal bandwidth loss as dictated by the number of snapshots taken. The multi-snapshot structured decomposition given here allows one to analytically shape the measured space with optimal noise characteristics and minimum system complexity. A two-snapshot system can measure a premeditated set of 14 reconstructables; we provide the null space for the subset of optimal systems that also achieve better SNR than the baseline single-snapshot system. A three-snapshot system can measure all 16 Mueller elements while offering an overall 26.3% or 50.4% better bandwidth-SNR figure of merit for the spectral and spatial systems, respectively. Finally, four-snapshot systems provide diminishing returns, but may be more implementable.

Channeled polarimeters modulate the Stokes parameters onto harmonic carriers of a particular independent domain such as time, space, wavenumber, or angle of incidence. Because the modulation creates many channels within the frequency sampling space of the detector array, channel bandwidth is crucial for this type of device. Much researches has been conducted to exploit more bandwidth in polarimeters that modulate in space, time, or wavenumber along. Our group and others have provided previous theoretical designs for hybrid-domain modulation strategies in order to extend the distance between channels in the Fourier domain through a bandwidth tradeoff approachin order to provide a wider channel bandwidth than systems utilize only one of the corresponding domains. This paper will present results from a a spatio-temporally modulated Stokes polarimeter. The system trades off the bandwidth between space and time to obtain further channel separations. In this work, we demonstrate the system implementation and the experiment results. The experiment compared the spatio-temporal hybrid domain modulated Stokes polarimeter with the spatial and temporal domain only modulated Stokes polarimeter to verify the prediction from the theoretical work. The experimental results indicated that comparing to the spatial and temporal domain only modulated Stokes polarimeters the hybrid-domain modulated polarimeter provides a better image reconstruction and contrast on signals with moderate bandwidth extension. We also consider adaptive reconstruction methods that allow the reconstruction filters to be tailored to the input data. This strategy will allow the bandwidth of the system to be optimally exploited for any particular task.

A multiple linear regression wind radii model developed in the North Atlantic basin based on the deviation angle variance technique was applied in the Australian region. The model was used to improve the historic database of 34-, 50- and 64-kt tropical cyclone (TC) wind radii estimates (R34, R50, and R64) for 374 TCs during the geostationary satellite era. Results during 2010-2016 produced quadrant mean absolute errors ranging between 49 and 61 km for the 34-kt radii, between 24 and 37 km for the 50-kt radii and between 20 and 25 km for the 64-kt radii.

This study aims to quantify the portion of the Earth's outgoing radiation that is attributable to tropical cyclones (TCs). To accomplish this, we have developed a method that starts with an image processing algorithm which labels cloud pixels associated with a TC, based on the time series of brightness temperature images and best-track data. The labels attributable to the TC are then combined with radiation data to obtain the TC-related radiation throughout its lifetime. Preliminary results are shown for the North Atlantic Ocean in 2012 and 2013: In 2012, the average TC shortwave and longwave radiation contributed 0.039 PW (or 0.35%) and 0.099 PW (or 0.34%), respectively, to the total regional radiation; In 2013, the contribution due tot TCs decreased to 0.022 PW (or 0.19%) for SW, and 0.059 PW (or 0.20%) for LW radiation.

The structure of planetary surfaces unveils basic formation processes and evolution lines of different objects in the solar system, and often the view on the top of a planet is the only available information about it. Advanced remote sensing technologies on deep space missions are aimed at accessing a maximum of relevant data to characterize a planetary object holistically. This approach requires concert strategies in planetary and engineering science. In this framework VIS/IR spectroscopic remote sensing methods are key technologies for imaging planetary atmospheres and surfaces, for studying their composition, texture, structure and dynamics. Basing on these analyses it succeeds to observe the single objects in more global geo-scientific content. The paper focuses on main geo-scientific output coming from spectroscopic studies of planetary surfaces in conjunction with their interiors, atmospheres, and the interplanetary space. It summarizes selected results of spectral studies onboard of the ESA deep space missions BepiColombo, Venus Express, Mars Express, and Rosetta. The corresponding spectral instruments are introduced. The complex conflation of special knowledge of the disciplines planetology, optical and IR measuring techniques, and space flight engineering is demonstrated in several examples. Finally, the paper gives an outlook of current developments for spectral studies in planned missions, and sums up some of the driving questions in planetary science.

The visualization of polarimetric data is often done by color mapping the linear parameters using the three channels in the HSV color space. Because this color space is not an accurate model of human color perception, the resulting visualization mixes the perceptual channels and contains nonuniformity. To the best of our knowledge, we present a new mapping strategy that reliably and accurately depicts reality by placing the polarization parameters directly into the perceptually uniform channels of CAM02-UCS. This mapping also ensures that regions of high polarization will be more visible, even when the measured irradiance is low.

We present the analysis and design of spatio-temporal channeled Stokes polarimeters. We extend our recent work on optimal pixelated polarizer arrays by utilizing temporal carrier generation, resulting in polarimeters that achieve super-resolution via the tradeoff between spatial bandwidth and temporal bandwidth. Utilizing the channel space description, we present a linear-Stokes design and two full-Stokes imaging polarimeter designs that have the potential to operate at the full frame rate of the imaging sensor of the system by using hybrid spatio-temporal carriers. If the objects are not spatially bandlimited, the achievable temporal bandwidth is more difficult to analyze; however, a spatio-temporal tradeoff still exists.

Little publicly available data exists for polarimetric measurements. When designing task specific polarimetric systems, the statistical properties of the task specific data becomes important. Until better polarimetric datasets are available to deduce statistics from, the statistics must be simulated to test instrument performance. Most imaged scenes have been shown to follow a power law power spectral density distribution, for both natural and city scenes. Furthermore, imaged data appears to follow a power law power spectral distribution temporally. We are interested in generating image sets which change over time, and at the same time are correlated between different components (spectral or polarimetric). In this brief communication, we present a framework and provide code to generate such data.

Micropolarizer arrays are occasionally used in partial Stokes, full Stokes, and Mueller matrix polarimeters. When treating modulated polarimeters as linear systems, specific assumptions are made about the Dirac delta functional forms generated in the channel space by micropolarizer arrays. These assumptions are 1) infinitely fine sampling both spatially and temporally and 2) infinite array sizes. When these assumptions are lifted and the physical channel shapes are computed, channel shapes become dependent on both the physical pixel area and shape, as well as the array size. We show that under certain circumstances the Dirac delta function approximation is not valid, and give some bounding terms to compute when the approximation is valid, i.e., which array and pixel sizes must be used for the Dirac delta function approximation to hold. Additionally, we show how the physical channel shape changes as a function of array and pixel size, for a conventional 0°, 45°, −45°, 90° superpixel micropolarizer array configuration.