Atmospheric outer scale profiling for wide-field adaptive optics

所有主要的地面观测站都配备了自适应光学系统，以补偿大气湍流造成的图像失真。克服湍流的影响，使地面望远镜能够照例击败天基望远镜的空间分辨率。对于下一代直径30-40米的“超大型”望远镜来说，望远镜结构、大气表层和自适应光学系统之间的相互作用变得复杂起来。现有的大气湍流模型描述了一个特征的外尺度，它限制了最大空间尺度上折射率波动的幅度。对于超大型望远镜来说，外部尺度的时变对自适应光学和望远镜控制的影响可能会严重降低图像质量，并限制可观测天空的比例。外部尺度的表征是剖面图中最大的悬而未决的问题，因为它不容易从望远镜误差中解脱出来。该项目的目的是描述望远镜局部环境中湍流通常最强烈的外部尺度，并评估这对下一代自适应光学仪器性能的影响。

All major ground-based observatories are equipped with adaptive optics systems to compensate for image distortion caused by atmospheric turbulence. Overcoming the effects of turbulence allows ground-based telescopes to routinely beat the spatial resolving power of their space-based counterparts. For the next generation of 30-40m diameter 'extremely large' telescopes the interaction between the telescope structure, the surface layers of the atmosphere and the adaptive optics system becomes complex. Existing models of atmospheric turbulence describe a characteristic outer scale that constrains the magnitude of refractive index fluctuations across the largest spatial scales. For extremely large telescopes, the impact of a time-varying outer scale on adaptive optics and telescope control can severely degrade image quality and limits the fraction of the observable sky. Characterisation of the outer scale is the biggest unsolved problem in profiling as it cannot be easily disentangled from telescope errors. The aim of this project is to characterise the outer scale in the local environment of the telescope where turbulence is typically strongest and assess the impact of this on the performance of the next generation of adaptive optics instruments.