太阳Lyman-α光谱观测新技术研究

The observation of the solar Lyman-α spectrum has become an international hot spot of the current study. Traditional filter imager cannot achieve the fine observation of the spectrum. Slit spectrometer has high spectral resolution, however, with poor signal-to-noise ratio, does not have Real-time Performance. Fourier transform spectrometer not only has both high spectral resolution and signal-to-noise ratio, but also can perform real-time imaging observations of the sun. The project, based on Fourier transform spectroscopy, proposes a real-time technique, with diffraction-interference and ultra-high spectral resolution, to observe the solar Lyman-α spectrum. This technique using the grating ±1spectral characteristics of the diffraction, taking the device as beam splitter and combiner, can avoid the difficult problem of developing the Fourier transform spectrometer beam splitter in band Lyman-α, thus the instrument can achieve interference imaging. This project intends to develop the critical technology that can achieve the observation of the solar Lyman-α spectrum with diffraction-interference and ultra-high spectral resolution by theoretical studies, system design and experimental validation. This will lay the theoretical and technical basis for the application of interference spectrum detection technology in space remote sensing instrumentation and have an important application value and significance for Chinese solar physics and space environmental exploration.

目前，国际上对太阳Lyman-α光谱的观测已经成为研究热点。传统滤光片式成像仪无法实现光谱的精细观测，狭缝光谱仪光谱分辨率高，但信噪比差、不具有实时性。干涉光谱仪具有较高的光谱分辨率与信噪比，而且能够对太阳进行实时成像观测。本项目基于傅里叶变换光谱技术，提出了一种用于观测太阳Lyman-α光谱的衍射-干涉混合超高光谱分辨实时观测技术，利用衍射光栅±1级光谱特性，将其作为分束与合束器件，这避免了在Lyman-α波段干涉光谱仪分束器研制困难的问题，使仪器能够实现干涉成像。拟通过理论研究、系统设计与实验验证攻克太阳Lyman-α光谱衍射-干涉混合超高光谱分辨观测的关键技术，这将为干涉光谱探测技术在空间遥感仪器应用奠定理论和技术基础，对我国太阳物理、空间环境探测具有重要的应用价值与研究意义。

本项目基于傅里叶变换光谱技术，提出了一种用于观测太阳Lyman-α光谱的衍射-干涉混合超高光谱分辨实时观测技术。根据太阳探测要求，确定太阳lyman干涉光谱探测仪技术指标，并对光学系统进行了仿真设计，采用离轴抛作为望远系统，利用衍射光栅±1级光谱特性，将其作为分束与合束器件，最后通过离轴抛物镜，OPD变化范围1mm，光谱分辨力达24000/12000，对应光谱分辨率0.005nm/0.01nm。根据前期在轨仪器方案，摸索真空紫外反射膜工艺，采用Al做反射基底，蒸镀λ/4厚MgF2，真空度达到10-8Pa，最终可实现121.6nm反射率可达80%。项目建立光栅±1光谱测量系统，并完成光栅分束与合束实验验证(@253nm)。在反射镜精度控制方面，根据条纹计数控制动镜位置，动镜采用多次反射结构，缩比光程，保证定位精度。动镜伺服采用补偿控制系统，确保其在扫描时采样平稳，经实验分析。半小时内条纹漂移0.1μm，10秒内条纹漂移5nm。这些研究工作为空间太阳观测仪器的发展提供了初步方案及技术研究基础。项目执行期间，共发表学术论文5篇。