Title：High-precision Astrometry (高精度天体测量)
Speaker：周建锋，清华大学工程物理系副教授、博导，宁波星帆信息科技有限公司创始人、总经理
Time：2021年11月5日（周五）10:00
Location:天文大厦三楼大会议室 (Large conference room, 3rd floor)

Abstract：
For a long time, it has been generally believed that the accuracy of astrometry is mainly restricted by the resolution of the telescope. At the beginning of the 21st century, Mike Shao of Caltech pointed out that the Point Spread Function (PSF) of a telescope can be accurately reconstructed under the premise that the image satisfies the Nyquist sampling criteria. Accurate PSF can significantly improve the accuracy of the astrometry. For example, the measurement of a 1-meter telescope can reach micro-arcsecond accuracy. In the past ten years, our group has completed three main tasks in high-precision astrometry. 1. We found a strict correction formula that converts the CCD/CMOS integral sampling image into an impulse sampling image to achieve a true and accurate PSF reconstruction; 2. We proposed the field distortion model based on the Fredholm integral, which unifies the distortion of an imaging system and the non-uniformity of CCD/CMOS sensors. It can describe the point-to-point position distortion and the deformation of the PSF; 3. Establish an accurate image matching algorithm, including translation and rotation. With these efforts, we have developed applications such as Adaptive Image Stabilization (AIS) systems and ultra-high-precision dimensional measurement for machine vision in the industrial field. In the field of space astrometry, we propose a three-step approach to achieve related applications and scientific goals. The first step is to develop a star tracker with a diameter of about 5 cm to improve the attitude measurement of the spacecraft to milli-arcsecond level. The second step is to develop a wide-field astrometric and photometric telescope with a diameter of about 30 cm, which is launched into the earth orbit, verify the relevant key technologies, the measurement accuracy is about ten micro-arcseconds. The third step is to develop a wide-field astrometric and photometric telescope with an aperture of about 2m and launch it to the second Lagrangian (L2) point. The measurement accuracy can reach 0.1 micro-arcseconds, mainly used to detect extrasolar terrestrial planets, measure the property of the dark energy and dark matter distribution in the universe, and so on.

长期以来，人们普遍认为天体测量的精度主要受望远镜分辨率的限制。21世纪初，加州理工学院的Mike Shao指出，在图像满足奈奎斯特采样准则的前提下，可以精确重建望远镜的点扩展函数（PSF）。精确的PSF可以显着提高天体测量的精度。例如，1米望远镜的测量可以达到微角秒精度。十年来，我们课题组在高精度天体测量方面完成了三项主要任务。 1、我们找到了严格的校正公式，将CCD/CMOS积分采样图像转换为脉冲采样图像，实现真正准确的PSF重建； 2.我们提出了基于Fredholm积分的视场畸变模型，它统一了成像系统的畸变和CCD/CMOS传感器的非均匀性。可以描述点对点的位置畸变和PSF的变形；3. 建立精确的图像匹配算法，包含了平移和旋转。借助这些工作，我们在工业领域开发了自适应图像稳定（AIS）系统和机器视觉超高精度尺寸测量等应用。在空间天体测量领域，我们提出了一个三步走的策略来实现相关的应用和科学目标。第一步是研制口径约5厘米的星敏感器，将航天器的姿态测量精度提高到毫角秒量级。第二步是研制直径约30厘米的宽视场天体测量及测光望远镜，发射到地球轨道，验证相关关键技术，测量精度约10微角秒。第三步，研制口径约2m的宽视场天体测量和测光望远镜，发射到第二拉格朗日（L2）点。测量精度可达0.1微角秒，主要用于探测太阳系外类地行星，测量宇宙中暗能量的性质和暗物质的分布等等。

个人简介：
周建锋，清华大学工程物理系副教授、博导，宁波星帆信息科技有限公司创始人、总经理。国际天文学联合会（IAU）会员，中国天文学会会员。国际期刊Applied Optics、JCS、RAA和多个国内核心期刊审稿人；负责3项国家自然科学基金课题，负责1项教育部自主科研重点项目，参加3项国家973、863项目。发表论文40余篇、授权发明专利15余项。2001～2017，历时17年参加我国重大空间科学项目硬X射线调制望远镜（HXMT），为DDM子系统及巡天成像子系统负责人。2014～至今，获得宁波3315项目和奉化区凤麓英才项目资助，创立星帆科技，致力于超高精度工业视觉测量技术，以及人工智能视觉检测设备的开发与销售。