AI 中文总结
针对水汽视宁降低ELT/METIS高对比度性能的问题，该研究分析其波前误差影响，提出基于非对称光瞳和深度学习的焦平面波前控制算法以缓解效应，提升性能。
AI 中文摘要
中红外极大望远镜（ELT）成像仪和光谱仪（METIS）将配备SCAO系统，在亮星的L波段（3.5-4.1μm）提供斯特列尔比高于90%，在N波段（8-13μm）接近99%。然而，用于高对比度成像的METIS日冕仪模块实际观测到的波前质量会受水汽视宁显著影响，该效应会在中红外波段给干空气视宁添加强色差分量。我们分析了两年的VLTI/GRAVITY fringe tracker档案，评估ELT尺度下毫秒级差分水汽柱密度的变化性。分析显示，水汽视宁会在N波段添加约175nm RMS的中位波前误差，主要由低阶像差构成，其中约150nm RMS为倾斜误差；若不校正，该效应会使可实现的对比度灵敏度极限降低超过两个星等。为缓解此效应，我们计划部署基于非对称光瞳的焦平面波前传感与控制算法，采用深度学习方法。在简要讨论焦平面波前控制对METIS的实际影响后，我们对比了有无焦平面波前控制时的预期高对比度成像性能。
英文摘要
The Mid-infrared ELT Imager and Spectrograph (METIS) will be equipped with a SCAO system delivering Strehl ratios above 90% at L band (3.5 - 4.1 um) and close to 99% at N band (8 - 13 um) on bright stars. Yet, the actual wavefront quality seen by the METIS coronagraphic modules used for high-contrast imaging will be significantly affected by water vapour seeing, which add a strong chromatic component to dry air seeing in the mid-infrared. We analysed two years of VLTI/GRAVITY fringe tracker archives to assess the variability of differential water vapour column density at millisecond timescales on ELT scales. Our analysis suggests that water vapour seeing will add a median wavefront error of about 175 nm rms at N band, consisting mostly of low-order aberrations, with around 150 nm rms of tip-tilt errors. If not corrected, this effect would degrade the achievable sensitivity limits in terms of contrast by more than two magnitudes. To mitigate this effect, we plan to deploy a focal-plane wavefront sensing and control algorithm based on an asymmetric pupil using a deep learning approach. After briefly discussing the practical impacts of focal-plane wavefront control in METIS, we compare the expected high-contrast imaging performance with and without focal-plane wavefront control.
Comments8 pages, paper presented at SPIE Astronomical Telescopes + Instrumentation 2026
Journal refProceedings of the SPIE, Volume 14150, id. 14150-372 (2026)
