Twilight and the Naked-Eye Observer: Models and High- Resolution Measurements

[摘要]本提案为微光光学遥感提供研究支持。像许多其他研究人员一样，我们对利用黄昏的光学结构来评估大气散射模型的真实性很感兴趣。然而，与其他系统不同的是，我们建议使用遥感系统进行测试，该系统结合了：a)具有宽带的多光谱通道，以及b)非常高的空间和时间分辨率。这种遥感系统是人类的三色视觉，它有明显的缺点，本质上是主观的。然而，色彩视觉的三色类似物，如彩色胶片和数字成像系统，让我们将它们的客观和可复制的反应映射到典型的肉眼观察者的反应中。利用摄影和数字成像技术获得的其他优势包括：a)同时分析大部分（或全部）暮光的光谱，b)以非常高的分辨率分析暮光光谱的时间演变，以及c)暮光偏振的空间细节。具体来说，我们计划使用彩色幻灯片的数字图像分析，偶尔通过光谱辐射测定法加以证实，以探索暮光的光度、偏振和比色结构。利用各种数据反演技术，我们将评估各种大气散射模型如何很好地解释裸眼观测者所看到的黄昏（我们在这里包括配备简单线性偏振器的观测者）。过去，由于黄昏的短暂性，研究人员只能收集有限数量的光度和偏振数据，而且通常只能作为构建大气探测的手段。暮光的比色学研究就更少了。虽然黄昏大气探测很有价值，但我们在这里提出了一个完全不同的目标：测量和模拟黄昏基本上无法量化的视觉结构。

Fraser/Abstract This proposal requests research support for optical remote sensing of twilight. Like many other researchers, we are interested in using twilight's optical structure to evaluate the verisimilitude of atmospheric scattering models. However, unlike others, we propose to do our testing with a remote sensing system that combines: a) multiple spectral channels with broad bandwidths, and b) very high spatial and temporal resolutions. This remote sensing system is human trichromatic color vision, which has the obvious disadvantage that it is essentially subjective. However, trichromatic analogues of color vision, such as color film and digital imaging systems, let us map their objective and reproducible responses into those of a typical naked- eye observer. Other advantages gained by using photography and digital imaging include the ability to easily analyze: a) spectra from large portions (or all) of the twilight at once, b) the temporal evolution of twilight spectra at very high resolutions, and c) the spatial details of twilight polarization. Specifically, we plan to use digital image analysis of color slides, occasionally corroborated by spectroradiometry, to explore the photometric, polarimetric, and colorimetric structure of twilight. With a variety of data inversion techniques, we will then assess how well various atmospheric scattering models account for twilight as seen by the naked-eye observer (we include here observers equipped with simple linear polarizers). In the past, twilight's ephemeral nature has restricted researchers to gathering only limited amounts of photometric and polarimetric data, and then usually only as a means of constructing atmospheric soundings. Colorimetric studies of twilight are even rarer. As worthwhile as twilight-derived atmospheric soundings are, here we propose a quite different goal: measuring and modeling twilight's largely unquantified visual structure.