星载电离层探测远紫外成像光谱仪关键技术研究

Far ultraviolet imaging spectrometer by satellite is one of the most important instruments for ionosphere observation and the mainstream trend of development. Our country is trying to enlarge the theory study and technological innovation of the ionosphere observation to solve the problem that the limitation of the present technique of far ultraviolet optical devices at home and abroad. Two key techniques of the sort of instrument design will be studied, the building of the far ultraviolet spectral radiant transmission model of targets of ionosphere, and the high performances design of the optical system of far ultraviolet imaging spectrometer. Based on data of foreign instruments and the modeling of dynamic ionosphere model (TIMEGCM), the far ultraviolet spectral radiant transmission model will be built by the simulation of secondary forward modeling and experiment. It applies scientific observation basis and parameters of performances to the design of imaging spectrometer with requisitions of the ionosphere scientific study and ionosphere weather application. The tandem gratings optical system will be chosen based on the characteristic that it would largely increase the spectral resolution without increasing the complexity of optical system and decreasing the system sensitivity under the limitation of the present technique of far ultraviolet optical devices. The tandem gratings secondary dispersive theory, the aberration theory, the geometric optical path differential analysis theory and the genetic algorithm will be utilized in the optimization of the tandem gratings spectrometer. The research will obtain an advanced far ultraviolet imaging spectrometer design for the ionosphere observation by satellite, which has the spectral resolution ≤ 1 nm, the spatial resolution ≤ 1.5 mrad, and a large field of view in the waveband of 115~180 nm. The ideology would solve the problem that the design with high performances is hardly realized in the simple optical system with high sensitivity. The investigation would provide unique tandem gratings far ultraviolet imaging spectrometer with international advanced level for the ionosphere observation, and important technique basis for the future development of instruments such as the prototype and engineering application.

星载远紫外成像光谱仪是电离层光学遥感的重要仪器之一。为突破远紫外光学器件技术的国外封锁和国内瓶颈，我国加大了电离层遥感的理论研究和技术创新。本项目主要对该光谱仪设计中的两个关键技术开展研究。基于电离层物理模型(TIMEGCM等)和国外仪器观测数据，模拟研究电离层远紫外光谱辐射传输特性模型；结合电离层科学研究和天气应用需求，提出仪器观测依据和设计指标。利用串联光栅系统在保持系统简单性和灵敏度的同时提高光谱分辨率的特性，综合二次色散理论，像差理论，几何光程微分理论和遗传算法对基于该系统的光学设计方案进行优化，提出在115~180 nm波段光谱分辨率优于1 nm，空间分辨率优于1.5 mrad的大视场远紫外成像光谱仪光学系统设计，解决简单光学系统在高灵敏度下难以实现高性能设计的问题。该设计将具有国际先进指标水平和独特的串联光栅成像光学系统，并为未来仪器的物理样机和工程化奠定关键技术基础。

星载远紫外成像光谱仪是电离层光学遥感的重要仪器，针对我国相关仪器系统设计与电离层空间物理结合较少，缺少远紫外空间辐射传输模型和反演科学需求指导的现状，以及受国内技术落后和国外技术封锁而使得光学系统设计性能大大受限的问题，本项目开展了以下关键技术研究，完成了预定的研究内容，实现了相关研究目标。在国外先进载荷GUVI的观测数据基础之上，对电离层远紫外波段观测的主要成分在白昼和夜间的特征光谱辐射光学模型进行了计算模拟，结合电离层物理模型正演统计分析获取了115 - 180 nm波段的电离层平均光谱辐射强度分布，以及其随地磁活动的变化特性，并总结了电离层远紫外波段特征辐射的多个特点。结合各特征波长的辐射强度，在地面利用实验室已有的各项标准设备，进行了模拟原理分析和辐射强度模拟实验，获取了地面的空间电离层远紫外特征光谱辐射的模拟结果，为远紫外成像光谱仪提供了灵敏度和信噪比测试时的动态信号模拟能力。根据电离层中主要观测粒子的探测需求和分布特征，结合830km的太阳同步轨道，设计了临边结合天底观测的探测模式，可实现50 - 500km高度部分侧向临边和天底整个条带的覆盖观测。结合计算分析得到的远紫外光谱空间辐射模型，预估了仪器系统灵敏度，并结合远紫外楔形阳极二维成像探测器性能参数，进行了130.4 nm，135.6 nm以及140 - 180 nm波段的仪器信噪比估算，为仪器系统设计奠定了基础。综合分析了远紫外波段特殊性导致的成像光谱仪光学系统设计的特殊性，提出了使用离轴抛物镜为望远系统，准直镜为离轴抛物镜，平面光栅串联凹面光栅为色散成像部分的反射式系统结构。对系统在宽谱段上进行像差校正的最优成像条件进行了分析计算，最终得到了在远紫外波段焦距135 mm，空间分辨率优于1 mrad，光谱分辨率0.6 nm的远紫外成像光谱仪光学系统设计，为将来的仪器研制奠定了重要的设计理论基础。