Adaptive Optics Sky Coverage Calculations for the Gemini‐North Telescope
Adaptive Optics Sky Coverage Calculations for the Gemini‐North Telescope
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DOI：
10.1086/316120
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发表时间：
1998-02
影响因子：
3.5
通讯作者：
B. Ellerbroek;D. Tyler
中科院分区：
文献类型：
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作者：
B. Ellerbroek;D. Tyler
天空覆盖的结果，提出了几个自然引导星星（NGS）和激光引导星星（LGS）自适应光学（AO）配置使用场景，望远镜，和AO设计参数来自双子座北8米望远镜。“天空覆盖”被定义为AO系统提供有用性能水平的天空部分，在这种情况下，在J、H或K波段具有高Strehl比。本研究中考虑的一些因素包括AO波前重建算法和控制带宽的优化、风震引起的倾斜/倾斜抖动的影响以及AO系统的变形镜（DM）和波前传感器（WFS）与Gemini-North站点的主视宁层的共轭。还考虑了高阶自适应光学对倾斜/倾斜制导星星像的补偿程度。在中间层钠层中使用单个信标的LGS AO通常相对于NGS AO将天空覆盖范围提高约一个数量级，主要是因为当其图像通过LGS高阶补偿锐化时，非常暗淡的自然引导星星足以用于倾斜/倾斜感测。对于NGS和LGS AO系统，风震、视宁度、天顶角以及DM和WFS的共轭范围的假设值也对估计的天空覆盖范围有非常显著的影响。这些因素中的前三个将需要通过基于队列的观察的调度算法来考虑。
Sky coverage results are presented for several natural guide star (NGS) and laser guide star (LGS) adaptive optics (AO) configurations using scenario, telescope, and AO design parameters derived from the Gemini‐North 8 m telescope. “Sky coverage” is defined as that fraction of the sky over which the AO system provides a useful level of performance, in this case a high Strehl ratio in the J, H, or K band. Some of the factors considered in this study include optimization of the AO wavefront reconstruction algorithm and control bandwidth, the effect of windshake‐induced tip/tilt jitter, and the conjugation of the AO system's deformable mirror (DM) and wavefront sensor (WFS) to the dominant seeing layer at the Gemini‐North site. The degree of compensation of the tip/tilt guide star image by the higher order adaptive optics is also considered. LGS AO using a single beacon in the mesospheric sodium layer typically improves sky coverage by about an order of magnitude relative to NGS AO, principally because a very dim natural guide star is sufficient for tip/tilt sensing when its image is sharpened by LGS higher order compensation. The values assumed for windshake, seeing, zenith angle, and the conjugate range of the DM and WFS also have a highly significant effect upon the estimated sky coverage for both the NGS and the LGS AO systems. The first three of these factors will need to be considered by scheduling algorithms for queue‐based observing.