Measuring and calibration non common path aberrations in adaptive optics assisted image-slicer based spectrographs

DPhil项目是ESO超大型望远镜(ELT)仪器开发的一部分，即开发第一光、自适应光学辅助积分场光谱仪HARMONII在Harmoni的背景下，E-ELT的积分场光谱仪，这个DPhil项目涉及一种称为非公共路径像差(NCPA)的像差的校准。NCPA是由自适应光学系统(AO)中用于波前传感的科学光和光之间的光路差异引起的。用于NCPA校准的最先进的技术之一是相位分集(PD)，它使用一对聚焦和散焦的图像来估计波前像差，使用最大似然方法和光在光学系统中的传播模型。HARMONI包含一个被称为图像切割器的光学部件，其作用是将输入的2D视场切片成可以馈送到光谱仪的长缝。这在使用诸如PD之类的技术时提出了挑战，因为尚未深入描述存在散焦时图像切割器的行为。图像切割器对光传播的影响，这是传统技术所不能考虑的，可能会对NCPA校准产生潜在的影响。在这种情况下，本研究项目的总体目标可以概括为：(1)提高对图像切割器对光传播影响的理解(2)表征最先进的NCPA校准技术在图像切割器存在的情况下的行为。这将有助于我们了解它们对Harmoni仪器的局限性和适用性。有可能修改这些技术以纳入图像切片器效应(3)开发NCPA校准的替代技术，以绕过最先进算法的缺点(4)实验工作：用实验基准演示和验证这些发现HARMONI是一台设备仪器，将解决观测天体物理学中的各种问题。这些都直接关系到STFC三个科学挑战中的两个：(B)恒星和行星系统是如何发展的，它们如何支持生命的存在？和(A)宇宙是如何开始的，它是如何演化的？这项研究属于PPAN的职权范围，它是“天文学和空间科学”研究领域的一部分。

The DPhil Project is part of the instrument development for ESO's Extrmely Large Telescope (ELT), namely the development of the first light, adaptive optics assisted, integral field spectrograph, HARMONIIn the context of HARMONI, the integral-field spectrograph for the E-ELT, this DPhil project deals with the calibration of a type of aberrations known as non-common path aberrations (NCPA). NCPA are caused by the difference in optical path between the science light and the light used for wavefront sensing within the Adaptive Optics system (AO). One of the most widespread state-of-the-art techniques for NCPA calibration is Phase Diversity (PD), which uses a pair of in-focus and defocused images to estimate the wavefront aberrations using a maximum likelihood approach and a model of light propagation through the optical system.HARMONI contains an optical component known as an image slicer whose role is to slice the input 2D field of view into long slits that can be fed to the spectrograph. This poses a challenge when using techniques such as PD because the behaviour of image slicers in the presence of a defocus has not been characterised in depth. The effects of image slicers on light propagation, which traditional techniques do not account for, could potentially have an impact on NCPA calibration.In this context, the general goals for this research project can be summarised as:(1) Improve the understanding of the effects of image slicers on light propagation(2) Characterize the behaviour of state-of-the-art NCPA calibration techniques in the presence of image slicers. This would help us understand their limitations and applicability to the HARMONI instrument. Potentially modify those techniques to incorporate image slicer effects(3) Develop alternative techniques for NCPA calibration that could circumvent the drawbacks of state-of-the-art algorithms(4) Experimental work: demonstrate and validate these findings with an experimental benchHARMONI is a facility instrument, and will tackle a wide variety of questions in observational astrophysics. These have direct bearing on two of STFC's three science challenges: (B) How do stars and planetary systems develop and how do they support the existence of life? and (A) How did the Universe begin and how is it evolving?. This research falls with the PPAN remit, it is part of the "Astronomy and Space Sciences" research area.