A New Autocollimation Externally Occulted Coronagraph

doi:10.3788/gzxb20235205.0552214

CIOMP OpenIR

	A New Autocollimation Externally Occulted Coronagraph
	Y. Ding; H. Zhang; Y. Huang; T. Wang and W. Xu
	2023
发表期刊	Guangzi Xuebao/Acta Photonica Sinica
ISSN	10044213
卷号	52 期号:5
摘要	Coronal is the outermost layer of the solar atmosphere，which ranges from the chromosphere across several sun radii. Coronal Mass Ejections（CMEs）eject large amounts of magnetized plasma from the sun's atmosphere into interplanetary space，resulting in massive solar explosions. Especially when CMEs spreads to the vicinity of the earth，they will produce geomagnetic disturbances such as geomagnetic storms，ionospheric storms，auroras，which have a destructive impact on satellite operations and ground infrastructure，and are one of the main driving sources of disastrous weather in space. The corona has long been studied internationally. Observations of the corona and coronal mass ejections help to study the effects of the sun's magnetic field on the earth. Meanwhile，they can monitor the severe space weather events affecting the earth and solar-terrestrial space. To realize the corona and coronal mass ejections observation better，and make more precise observation angles. The solar alignment system is designed in this paper. The entrance pupil diameter of the system is 40 mm，the focal length is 360 mm and the field of view is 2 degrees. With alignment system imaging to the sun，the center coordinates of the solar image on the detector are read through the program，so as to judge whether the coronagraph is aligned with the sun，and the observation Angle of the coronagraph is adjusted according to the coordinate offset calculation. The solar alignment system was applied to the three-disk externally occulted coronagraph for the experiment. The main parameters of the coronagraph are as follows：the field of view is ±20 degrees；the pixel resolution is 1.2 arcmin；the pixel size is 13.5 μm；the wavelength is from 630 nm to 730 nm；the effective F-number is 4；the focal length is 38 mm；and the transfer function is greater than 0.6. Compared with the brightness of the solar photosphere，the brightness of the corona light is very weak，so the suppression of stray light is the key problem of the coronagraph system. Based on the observable range of field of view and corona brightness curve，the design requirements of stray light suppression level of coronagraph are given. The suppression ability of diffraction of external occulter was compared between single-disk occulter and three-disk occulter. The comparison chart of diffraction field intensity between single-disk occulter and three-disk occulter at the incident aperture is obtained by numerical calculation. Coronagraph usually works against a pure black cosmic background. When conducting experiments in the laboratory，as its space is limited，the reflected and scattered light hitting the walls and reaching the camera surface can affect the stray light suppression level detection. Therefore，a black hole detection method is proposed to detect the total stray light of the coronagraph. The black hole refers to the semi-open black box with black absorbing film inside. In the range of visible light，the absorbent film has a very low reflectance and a strong ability to absorb light，which can minimize the influence of ambient light during the experiment. Finally，the detection device is built，the camera is used to shoot the direct solar light image and the stray light image of the system，and the gray value is read in the software to calculate the stray light suppression level. The experimental results show that the pointing accuracy of the coronagraph reaches 0.11'，the diffraction stray light of the three-disk occulter is lower than the diffraction stray light of the single-disk occulter，and the suppression level of the total stray light of the coronagraph reaches 10-13 orders of magnitude. The stray light detection method has good results and high accuracy，and the alignment system has realized its expected function. © 2023 Chinese Optical Society. All rights reserved.
DOI	10.3788/gzxb20235205.0552214
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收录类别	ei
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文献类型	期刊论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/67436
专题	中国科学院长春光学精密机械与物理研究所
推荐引用方式 GB/T 7714	Y. Ding,H. Zhang,Y. Huang,et al. A New Autocollimation Externally Occulted Coronagraph[J]. Guangzi Xuebao/Acta Photonica Sinica,2023,52(5).
APA	Y. Ding,H. Zhang,Y. Huang,&T. Wang and W. Xu.(2023).A New Autocollimation Externally Occulted Coronagraph.Guangzi Xuebao/Acta Photonica Sinica,52(5).
MLA	Y. Ding,et al."A New Autocollimation Externally Occulted Coronagraph".Guangzi Xuebao/Acta Photonica Sinica 52.5(2023).

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