天基电离层气辉成像仿真分析研究

Simulation of Space Borne Ionospheric Airglow Imaging

通过气辉成像仪对电离层气辉进行探测,能够反映电离层中电子总含量、等离子体泡分布等特性,是有效的电离层探测方式之一。电离层的原子分子在白天吸收太阳辐射激发到较高能态,在夜间以气辉的形式将能量辐射出去,辐射强度与所参与反应的电离层成分密度等密切相关,因此气辉是用来观测电离层很好的示踪物。天基气辉成像方法具有全球范围观测的巨大优势,为了推动天基成像仪的设计研制和参数优化,丰富和扩展电离层探测手段,需要对全球气辉强度进行成像仿真分析。该研究主要工作:(1)分析了电离层夜间630 nm光化反应过程,设计了一种气辉成像仿真分析方法,该方法对630 nm辐射强度进行计算,分别获得了太阳活动高年和低年内四个不同季节的气辉单光谱信号源强度分布,为设定探测指标提供理论依据;(2)开展了630 nm气辉天底成像仿真研究,包括成像链路分析、信噪比分析,并使用一个时间延时积分成像的典型成像仪参数,开展结合卫星运行轨道的扫描成像仿真。本文主要结论:(1)夜间630 nm单光谱气辉强度与日间太阳辐射强度关系密切,太阳活动高年夜半球平均辐射强度为115 Rayleigh,太阳活动低年夜半球平均辐射强度为50 Rayleigh,辐射大小和分布符合卫星载荷GLO-1和国际空间站IMAP任务的实际观测结果;(2)典型参数成像仪天底观测幅宽达到245 km,气辉水平分辨率达到1 km,对强度大于50 Rayleigh气辉成像的信噪比优于10,在太阳活动高年能够清晰观测电离层气辉全球尺度结构,在太阳活动低年能够观测低纬地区电离层气辉结构。该研究结果可为天基电离层气辉成像探测提供理论依据,也可为其他辐射波段的气辉观测和成像仪参数设计优化提供参考。

The ionospheric characteristics such as total electron content and plasma bubble parameters can be retrieved by observing the ionospheric airglow with spaceborne imager.Atoms and molecules absorb solar radiation and excite to higher energy states in the daytime.At night,they radiate the energy in the form of airglow.The radiation intensity is related to the density of ionospheric components.Therefore,airglow is an excellent tracer for observing the ionosphere.In order to promote and optimize the design of space-borne imager and enrich the ionospheric detection methods,it is necessary to conduct imaging simulation analysis of global airglow.The main works of this paper are as follows:(1)the photochemical reaction process of 630 nm radiation at night is analyzed,and a simulation analysis method of airglow imaging is designed.The intensity distributions of airglow in four different seasons with high and low solar activity are obtained,which provide a theoretical basis for setting detection index;(2)the simulation research of space-borne imaging is carried out,including imaging chain and signal-to-noise ratio analysis.A typical imager parameter with a time-delay integral imaging method is used to carry out the simulation combined with the satellite orbit.The main conclusions are as follows:(1)the intensity of 630 nm at night is closely related to the solar radiation intensity in the daytime.The average night radiation intensity with high solar activity is 115 Rayleigh,and that with low solar activity is 50 Rayleigh,the radiation intensity and distribution are consistent with the actual observation results of GLO-1 and ISS-IMAP;(2)the observation width and horizontal resolution of typical parameter imager reach 245 km and 1 km.The signal-to-noise ratio is more significant than 10 for the intensity greater than 50 Rayleigh,it means the typical parameter imager can observe the global structure of ionospheric airglow with high solar activity.The research results in this paper provide a theoretical basis for space-borne ionospheric airglow detection and provide a reference for observing other wavelengths.