利用恒星图像诊断空间望远镜的失准和抖动
Diagnosing space telescope misalignment and jitter using stellar images
摘要：
望远镜的点扩散函数（PSF）的准确知识是必不可少的弱引力透镜的测量，持有宇宙学约束的巨大希望。对于太空望远镜，由于望远镜结构中的热漂移和/或由于航天器指向的抖动（地面望远镜有额外的变化来源），PSF可能会随时间变化。我们描述和模拟的过程中使用的恒星在每次曝光的图像，以确定的错位和抖动参数，并重建PSF在任何一点，在该曝光的视野。模拟使用SNAP（http：//www.example.com）望远镜的设计。snap.lbl.gov典型曝光中的恒星图像数据确定次级反射镜的位置，其精确度与$20 {\rm nm}$相同。PSF椭圆度和大小是弱透镜效应的感兴趣的量，在每次曝光中分别确定为$4.0 \times 10^{-4}$和$2.2 \times 10^{-4}$精度，足以满足弱透镜效应的要求。我们表明，对于空间望远镜的情况下，PSF估计误差的规模与从所有可用的恒星在曝光中收集的光子总数的平方根成反比。
英文摘要：
Accurate knowledge of the telescope's point spread function (PSF) is essential for the weak gravitational lensing measurements that hold great promise for cosmological constraints. For space telescopes, the PSF may vary with time due to thermal drifts in the telescope structure, and/or due to jitter in the spacecraft pointing (ground-based telescopes have additional sources of variation). We describe and simulate a procedure for using the images of the stars in each exposure to determine the misalignment and jitter parameters, and reconstruct the PSF at any point in that exposure's field of view. The simulation uses the design of the SNAP (http://snap.lbl.gov) telescope. Stellar-image data in a typical exposure determines secondary-mirror positions as precisely as $20 {\rm nm}$. The PSF ellipticities and size, which are the quantities of interest for weak lensing are determined to $4.0 \times 10^{-4}$ and $2.2 \times 10^{-4}$ accuracies respectively in each exposure, sufficient to meet weak-lensing requirements. We show that, for the case of a space telescope, the PSF estimation errors scale inversely with the square root of the total number of photons collected from all the usable stars in the exposure.
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