大气湍流对平流层星光导航中星光传输的影响

摘要

以平流层飞行器用星光导航为背景,研究在平流层内星光传输过程受大气湍流的影响机理,揭示平流层中星光的衰减规律,为建立平流层星光导航星库以及电耦合器件(CCD)所摄取的星图补偿方法提供理论依据.研究提出将流场密度和流场密度脉动变化大的区域划分为宽度为L的特性截面,并基于几何光学法及统计光学理论分别计算星光穿过各特性截面后产生的光线偏折及平均光强衰减,进而推导整个平流层内星光传输过程中的能量衰减变化曲线.采用基于κ-ε双方程湍流模型的雷诺平均法计算不同极端情况下的大气湍流场密度及密度脉动分布.通过计算机数值仿真表明:星光穿过具有湍流的平流层时将发生明显偏折,其偏折程度与流场密度值有关;同时星光光强衰减,衰减程度与流场密度脉动值有关.%Based on the satellite celestial navigation,this paper studies the mechanism of the starlight transmission in atmospheric turbulence in the stratosphere,reveals the attenuation law of the starlight during transmission,and provides the theoretical basis for establishing the navigation star database and the compensation algorithm of a charge coupled device (CCD) star map.Segments with a certain thickness is proposed by intercepting the sections at the boundary of which the density and density fluctuation of the turbulent field has changed seriously.At the mean time the deflection and average intensity of the starlight after transferring through each section is calculated respectively according to the geometrical optic method and the statistical optic theory,and then the energy attenuation curve of the starlight during transmission through the whote stratosphere is derived either.The k-ε turbulence model is adopted to simulate the density and density fluctuation field of the atmospheric turbulence in different extreme natural cases.The results of the simulation show that the starlight will be deflected obviously and the starlight intensity will decay after traveling through the stratosphere with turbulence,where its deflection and attenuation are related to the density and the density fluctuation of the turbulence,respectively.