A synthetic aperture radar (SAR) with hybrid-polarity (CL-pol) architecture transmits circular polarization and receives two orthogonal, mutually coherent linear polarizations, which is one manifestation of compact polarimetry. The resulting radar is relatively simple to implement and has unique self-calibration features and low susceptibility to noise. It also enables maintenance of a larger swath coverage than fully polarimetric SAR systems. A research team composed of various departments of the Government of Canada evaluated this compact polarimetry mode configuration for application to soil moisture estimation, crop identification, ship detection, and sea-ice classification. This paper presents an overview of compact polarimetry, the approach developed for evaluation, and preliminary results for applications important to the Government of Canada. The implications of the results are also discussed with respect to future SAR missions such as the Canadian RADARSAT Constellation Mission, the American DESD...

Compact polarimetry overview and applications assessment

The present article is an introductory paper in this special issue on synthetic aperture radar (SAR). A short review is presented on the recent trend and development of SAR and related techniques with selected topics, including the fields of applications, specifications of airborne and spaceborne SARs, and information contents in and interpretations of amplitude data, interferometric SAR (InSAR) data, and polarimetric SAR (PolSAR) data. The review is by no means extensive, and as such only brief summaries of of each selected topics and key references are provided. For further details, the readers are recommended to read the literature given in the references theirin.

Recent Trend and Advance of Synthetic Aperture Radar with Selected Topics

Compact polarimetry is a technique that allows construction of pseudo quad-pol information from dual-polarization synthetic aperture radar (SAR) systems. Compact polarimetry showed promise of being able to reduce the complexity, cost, mass, and data rate of a SAR system while attempting to maintain many capabilities of a fully polarimetric system. In this paper, we study different transmit/receive configurations to determine which polarimetric configurations allow for superior reconstruction of the fully polarimetric data. We discuss modifications of the original reconstruction algorithm proposed by Souyris , which show potential to better reconstruct fully polarimetric data.

Comparison of Compact Polarimetric Synthetic Aperture Radar Modes

The importance of land surface-atmosphere interactions, principally the effects of soil moisture, on hydrological, meteorological, and ecological processes has gained widespread recognition over recent decades. Its high spatial and temporal variability however, makes soil moisture a difficult parameter to measure and monitor effectively using traditional methods. Microwave remote sensing technology has demonstrated the potential to map and monitor relative soil moisture changes over large areas at regular intervals in time and also the opportunity of measuring, through inverse modelling, absolute soil moisture values. This ability has been demonstrated under a variety of topographic and land cover conditions using both active and passive microwave instruments. The purpose of this paper is to review the current status of soil moisture determination from active microwave remote sensing systems and to highlight the key areas of research that will have to be addressed to achieve routine use of the proposed retrieval approaches.

Soil moisture retrieval from active spaceborne microwave observations: an evaluation of current techniques.

[1] We introduce a new technique derived from the classical Stokes parameters for analysis of polarimetric radar astronomical data. This decomposition is based on m (the degree of polarization) and chi (the Poincare ellipticity parameter). Analysis of the crater Byrgius A demonstrates how m-chi can more easily differentiate materials within ejecta deposits and their relative thicknesses. We use Goldschmidt crater to demonstrate how m-chi can differentiate coherent deposits of water ice. Goldschmidt crater floor is found to be consistent with single bounce Bragg scattering suggesting the absence of water ice and further corroborating adsorbed H to mineral grains or an H2O frost as plausible explanations for a H2O/OH detection by near-infrared instruments.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2011JE003986

The m‐chi decomposition of hybrid dual‐polarimetric radar data with application to lunar craters

Recent interest in dual-pol SAR systems has lead to a novel approach to dual-pol SAR, the so-called compact polarimetric imaging mode. The original idea, presented by Souyris et al. [1], employed a SAR system transmitting a linearly polarized wave rotated by 45° with respect to the orientation of the vertical (V) and horizontal (H) receive antennas. One then constructed pseudo quad-pol data from the dual-pol data assuming reflection symmetry and a model relationship between the |HV| return and the HH-VV correlation coefficient. Recently Stacy and Preiss [2], and Nord et al. [3], presented extensions of the original dual-pol compact polarimetry ideas and, independently, Raney [4] has analyzed the Stokes parameters for dual-pol SAR systems. Here we briefly present the extensions of the original compact polarimetry ideas following the development in [3]. We then discuss the dual-pol signature plot and show that it provides a simple, visual means to assess the polarimetric content for any dual-pol SAR system that transmits a polarized wave of arbitrary ellipticity / orientation, and coherently receives any two orthogonal polarizations. Lastly, we consider the default dual-pol mode of ALOS PALSAR: H-transmit with coherent (V, H) receive. We provide an interpretation of the α-entropy plot for this (HH, HV) dual-pol data.

https://earth.esa.int/workshops/polinsar2007/papers/84_ainsworth.pdf

N.J.S. Stacy

Papers

Comparison of Compact Polarimetric Synthetic Aperture Radar Modes

Analysis of Compact Polarimetric SAR Imaging Modes