空间目标光谱特性研究进展

Advances in Spectroscopic Characters of Space Objects

空间目标光谱是空间目标光学特性的本质体现,能够反映空间目标的材质属性,通过将实验室测量的材质光谱与实测空间目标光谱进行匹配处理,可以识别目标的材质类型,有助于分析空间目标的类型及工作状态。针对空间目标光谱测量及材质信息反演问题,研究空间目标光谱形成原理、反演方法及红化效应等问题。结合空间目标的固体光谱特点,分析了振动光谱、电子光谱对350～2 500 nm谱段的贡献。对基于空间目标光谱开展目标材质识别的三种常用方法进行了概括,即人工神经网络法、粒子群优化法和频谱解混法,对常用的反射率及其导数、中心位移等特征参数进行了分析。研究了空间目标光谱的红化效应,指出红化效应是由部分氧化物进入空间后出现脱氧效应所致。部分含氧元素的空间目标材质进入空间后会出现氧元素从材质表面脱离的现象,脱氧后的材质会与空间环境中的污染物结合形成松散的化学键,此类化学键更易吸收长波波段的光能量,且波长越长越易被吸收,从而导致反射率斜率随波长增加而上升的红化效应。在极端空间环境的持续作用下,空间目标表面材质会出现化学变化、物理变化等老化问题,通过光谱观测能够对材质的老化情况进行分析,为及时修复现有卫星、补发替换卫星提供依据。

Spectroscopic characters of space objects are basic optical attributes which could stand for the material types of space objects.By comparing actual spectral characteristics with that obtained in the lab,the types of space materials can be identified,which is beneficial for the analysis of working states and compositions of space objects.Aiming at the problems of spectrum measurement and material information retrieval,the spectroscopic theory,retrieval methods and reddening effect of space objects spectrum are analyzed in this paper.The contributions on the spectrum from 350 to 2 500 run from vibrational spectrum and electrical spectrum are investigated based on solid spectrum characters.Three methods commonly used in space objects material identification based on spectrum characters are studied,which are artificial neural network algorithm,particle swarm optimization algorithm and spectrum unmixing algorithm,and the features including spectrum reflectance and its derivative,center displacement are discussed.Reddening effect in spectrum measurement is studied,and it is shown that the reddening effect is related to the deoxidizing effect when some material access to space environments.The loose chemical bonds are formed due to the separation of oxygen and the combination of contaminations in space,which results in more absorptions of light energy and the higher slope of reflectance at longer wavelength that is named reddening effect.The reflectance of spectrum can be used to analyze material aging problems on the surface of satellite material under the continuous influences of harsh space environment,including chemical or physical changes,which are favorable for repairing existing satellite or launching new satellite.