This paper describes the innovative optical design of the Metis coronagraph for the Solar Orbiter ESA-NASA mission. Metis is a multi-wavelength, externally occulted telescope for the imaging of the solar corona in both the visible and ultraviolet wavelength ranges. Metis adopts a novel occultation scheme for the solar disk, that we named “inverse external occulter”, for reducing the extremely high thermal load on the instrument at the spacecraft perihelion. The core of the Metis optical design is an aplanatic Gregorian telescope common to both the visible and ultraviolet channels. A suitable dichroic beam-splitter, optimized for transmitting a narrow-band in the ultraviolet (121.6 nm, HI Lyman-α) and reflecting a broadband in the visible (580–640 nm) spectral range, is used to separate the two optical paths. Along the visible light optical path, a liquid crystal electro-optical modulator, used for the first time in space, allows making polarimetric measurements.

中文翻译：

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用于太阳轨道飞行器任务的多波长成像日冕仪 Metis 的光学设计

本文介绍了用于太阳轨道飞行器 ESA-NASA 任务的 Metis 日冕仪的创新光学设计。Metis 是一种多波长、外部掩星望远镜，用于在可见光和紫外波长范围内对日冕进行成像。Metis 采用了一种新颖的太阳盘掩星方案，我们将其命名为“逆外部掩星”，以减少航天器近日点对仪器的极高热负荷。Metis 光学设计的核心是可见光和紫外线通道通用的消球差格里高利望远镜。一个合适的二向色分束器，优化用于传输紫外（121.6 nm，HI Lyman-α）中的窄带并反射可见光（580-640 nm）光谱范围内的宽带，用于分离两条光路. 沿着可见光光路，