|Time:||Monday, November 15, 2021, 03:00pm|
|Title:||High-precision Astrometry (高精度天体测量)|
|Speaker:||Dr. Jianfeng Zhou 周建锋|
S727 & Online via Zoom https://zoom.us/j/97724059098?pwd=SFBDM2dTUjJ0eUt3NkY2dTA5RU1Rdz09
Astrometry opened the era of modern astronomy/physics and plays a crucial role in contemporary astronomy, including the measurement of the three-dimensional structure of the Milky Way, black hole detection, and search for exoplanets, etc. High-precision astrometry has gone through three cognitive stages, from improving the telescope's resolution to the precise modeling of the point spread function (PSF) and then to the perfect reconstruction of the PSF.
In the past ten years, our group has completed three main tasks to make astrometric accuracy reach micro-arcsecond or even sub-micro-arcsecond level: 1. We have found a strict correction formula for the actual integral sampling image and the non-uniform response within pixels; 2. We propose a general field distortion model based on the Fredholm integral, which can fully describe the non-uniformity of the entire imaging system and significantly reduce the complexity of the calibration system; 3. We establish an image matching algorithm that includes accurate translation and rotation. With these efforts, we have developed adaptive image stabilization (AIS) systems and high-precision size measurement of machine vision in the industrial field. In space astrometry, we have proposed a three-step strategy to achieve related technical applications and scientific goals. The first step is to apply related technologies to the star tracker to measure a spacecraft's attitude to approach milli-arcsecond accuracy. The second step is to build a wide-field astrometric and photometric telescope with a diameter of about 30 cm and launch it into the earth's orbit. The measurement accuracy is about 10 micro-arcsecond. The third step is to construct a wide-field astrometric and photometric telescope with an aperture of about 2m and launch it to the second Lagrange (L2) point. The measurement accuracy can reach 0.1 micro-arcsecond. This telescope is aimed to detect terrestrial extrasolar planets and measure the nature of dark energy and the distribution of dark matter in the universe.
天体测量开启了现代天文学/物理学时代，也在当代天文学中发挥着至关重要的作用，包括银河系三维结构的测量、黑洞探测和系外行星搜索等等。高精度天体测量经历了三个认知阶段，从提高望远镜的分辨率到点扩散函数（PSF）的精确建模，再到点扩散函数的完美重建。在过去的十年中，我们课题组完成了三项主要任务，使天体测量精度能够达到微角秒甚至亚微角秒级：1、我们找到了实际积分采样图像和像素内非均匀响应的严格校正公式； 2、我们提出了一种基于Fredholm积分的通用视场畸变模型，可以完备描述整个成像系统的非均匀性，显着降低标定系统的复杂度； 3. 我们建立了一个包含精确平移和旋转的图像匹配算法。通过这些努力，我们在工业应用领域开发了自适应图像稳定 (AIS) 系统和机器视觉的高精度尺寸测量。在空间天体测量方面，我们提出了实现相关技术应用和科学目标的三步策略。第一步是将相关技术应用到型敏感器上，测量航天器的姿态，精度接近毫角秒。第二步是研制直径约30厘米的宽视场天体测光望远镜，并将其发射到地球轨道上。测量精度约为 10 微弧秒。第三步，研制口径约2m的宽视场天文测光望远镜，发射到第二个拉格朗日（L2）点。测量精度可达0.1微角秒。该望远镜旨在探测类地系外行星，并测量暗能量的性质和暗物质在宇宙中的分布。
Jianfeng Zhou received the B.Sc. degree in Geophysics from the University of Science and Technology of China in 1995, and the M.Sc. and Ph. D. degrees in Astrophysics from Shanghai Astronomical Observatory, Chinese Academy of Sciences, in 1998 and 2001, respectively. From 2001 to 2004, he was a post-doctoral researcher at the Center for Astrophysics at Tsinghua University in China and then joined the faculty in the engineering physics department. He is currently an Associate Professor. His technical interests include imaging and image reconstruction methods and astrophysics.
Host: Sharon Xuesong Wang