The polarization state of radar echoes from planetary bodies contains information about the scattering mechanisms present on the surface and thus the near-surface physical properties. Polarimetric radar scatter from complex surfaces, such as those observed for spacecraft-visited near-Earth asteroids (NEAs), is not well understood in terms of relating observed polarimetry to surface properties. Here we present an improved methodology for polarimetric analyses of ground-based radar observations of NEAs, extending techniques derived for larger bodies. We calculate the Stokes vector for delay-Doppler images of NEAs and use this to perform the m-chi decomposition and derive polarimetric products such as the degree of polarization, circular polarization ratio, and degree of linear polarization. We apply this methodology to radar observations of NEAs (53319) 1999 JM₈, (101955) Bennu, and (33342) 1998 WT₂₄ obtained by the Arecibo Observatory. We also perform numerical simulations of the m-chi decomposition for irregular boulders to augment the interpretation of the results for NEAs. Our analyses show that significant components of radar echoes are depolarized (random polarization) and linearly polarized. The numerical simulations confirm that depolarization is increased by single scattering from nonspherical wavelength-scale particles. Our analysis suggests that 1999 JM₈ is possibly covered in regolith and that surface scatterers dominate the scattering properties of Bennu. The NEA 1998 WT₂₄ displays diverse polarimetric properties, which we reconcile with optical and thermal observations by assuming a fine-grained regolith mantling a rugged, dense interior. In this work, we demonstrate the usefulness of radar polarimetry in characterizing the physical properties of planetary surfaces.

来自行星体的雷达回波的极化状态包含有关存在于地表的散射机制以及近地表物理特性的信息。在将观测到的极化与表面特性相关联方面，从复杂表面（例如对航天器访问过的近地小行星 (NEA) 观察到的那些表面）的极化雷达散射还不是很清楚。在这里，我们提出了一种改进的方法，用于对 NEA 的地基雷达观测进行极化分析，扩展了针对较大天体的衍生技术。我们计算 NEA 延迟多普勒图像的斯托克斯矢量，并使用它来执行m-chi分解并导出极化产物，例如极化程度、圆极化比率和线性极化程度。我们将此方法应用于由阿雷西博天文台获得的 NEA (53319) 1999 JM ₈、(101955) Bennu 和 (33342) 1998 WT _{24 的}雷达观测。我们还对不规则巨石的m-chi分解进行了数值模拟，以增强对 NEA 结果的解释。我们的分析表明，雷达回波的重要成分是去极化（随机极化）和线极化。数值模拟证实非球形波长尺度粒子的单次散射会增加去极化。我们的分析表明，1999 JM ₈可能被风化层覆盖，并且表面散射体主导了 Bennu 的散射特性。NEA 1998 WT ₂₄显示出不同的偏振特性，我们假设细粒风化层覆盖着坚固、致密的内部，从而与光学和热观测相一致。在这项工作中，我们展示了雷达极化测量在表征行星表面物理特性方面的有用性。