Spiders in Lyot Coronagraphs
Spiders in Lyot Coronagraphs
复制标题
利奥日冕仪中的蜘蛛
DOI：
10.1086/432903
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
J. Lloyd
中科院分区：
文献类型：
--
作者：
A. Sivaramakrishnan;J. Lloyd
原则上，日冕仪在无遮挡孔径望远镜上比在遮挡孔径望远镜上更容易抑制轴上恒星光。最近的设计，例如变迹光瞳 Lyot 日冕仪、“带限”Lyot 日冕仪以及相位掩模日冕仪的几种变体，在无遮挡的圆孔径望远镜上效果最佳。这些设计的开发是为了能够发现和表征附近的木星甚至类地系外行星。当今所有主要的天基和配备自适应光学器件的地面望远镜都是遮光孔径系统，带有由辅助支撑“蜘蛛”叶片固定到位的辅助镜。二次遮蔽的存在可以通过巧妙的日冕仪设计来解决，但蜘蛛叶片本身会产生衍射光，这可能会阻碍对附近恒星周围木星系外行星的搜索。我们研究了莱奥特日冕仪中抑制蜘蛛叶片衍射的问题，包括变迹光瞳和带限设计。我们展示了如何大幅减少蜘蛛叶片衍射，并且实际上将其包含在最终的冠状图像中，在焦平面掩膜掩蔽点的几何图像的一个分辨率元素内。这使得通过为双子座和甚大望远镜等 8-10 m 级望远镜开发的下一代自适应光学系统，对外木星进行自适应光学日冕搜索成为可能。
In principle, suppression of on-axis stellar light by a coronagraph is easier on an unobscured aperture telescope than on one with an obscured aperture. Recent designs such as the apodized pupil Lyot coronagraph, the "band-limited" Lyot coronagraph, and several variants of phase-mask coronagraphs work best on unobscured circular aperture telescopes. These designs were developed to enable the discovery and characterization of nearby Jovian or even terrestrial exoplanets. All of today's major space-based and adaptive optics-equipped ground-based telescopes are obscured-aperture systems with a secondary mirror held in place by secondary support "spider" vanes. The presence of a secondary obscuration can be dealt with by ingenious coronagraph designs, but the spider vanes themselves cause diffracted light, which can hamper the search for Jovian exoplanets around nearby stars. We look at the problem of suppressing spider vane diffraction in Lyot coronagraphs, including apodized pupil and band-limited designs. We show how spider vane diffraction can be reduced drastically and in fact contained in the final coronagraphic image, within one resolution element of the geometric image of the focal plane mask's occulting spot. This makes adaptive optics coronagraphic searches for exojupiters possible with the next generation of adaptive optics systems being developed for 8-10 m class telescopes such as Gemini and the Very Large Telescopes.