Abstract. Differential optical transfer function (dOTF) is an image-based, noniterative wavefront sensing method that uses two star images with a single small change in the pupil. We describe two possible methods for introducing the required pupil modification to the James Webb Space Telescope, one using a small (<λ/4) displacement of a single segment’s actuator and another that uses small misalignments of the NIRCam’s filter wheel. While both methods should work with NIRCam, the actuator method will allow both MIRI and NIRISS to be used for segment phasing, which is a new functionality. Since the actuator method requires only small displacements, it should provide a fast and safe phasing alternative that reduces the mission risk and can be performed frequently for alignment monitoring and maintenance. Since a single actuator modification can be seen by all three cameras, it should be possible to calibrate the non-common-path aberrations between them. Large segment discontinuities can be measured using dOTFs in two filter bands. Using two images of a star field, aberrations along multiple lines of sight through the telescope can be measured simultaneously. Also, since dOTF gives the pupil field amplitude as well as the phase, it could provide a first approximation or constraint to the planned iterative phase retrieval algorithms.

中文翻译：

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使用差分光学传递函数的James Webb空间望远镜分段定相

抽象的。差分光学传递函数（dOTF）是一种基于图像的非迭代波阵面传感方法，该方法使用两个星光图像，并且瞳孔有一个小的变化。我们介绍了两种可能的方法，可将所需的瞳孔修改引入James Webb空间望远镜，一种方法是使用单个段致动器的较小（<λ/ 4）位移，另一种方法是使用NIRCam滤光轮的较小偏差。虽然这两种方法都可以与NIRCam一起使用，但是执行器方法将允许MIRI和NIRISS都可以用于分段定相，这是一项新功能。由于执行器方法仅需要很小的位移，因此它应提供一种快速，安全的调相替代方案，从而降低执行任务的风险，并且可以经常执行以进行对准监控和维护。由于所有三个摄像机都可以看到单个执行器修改，因此应该可以校准它们之间的非公共路径像差。可以使用两个滤波器带中的dOTF来测量大的段不连续性。使用星空的两个图像，可以同时测量通过望远镜的多条视线的像差。而且，由于dOTF给出了瞳孔场的振幅以及相位，因此它可以为计划的迭代相位检索算法提供第一近似值或约束条件。