基于非局域热平衡模式的临近空间目标背景临边对比度模型

Model of near-space limb contrast based on non-local thermodynamics equilibrium model

对临近空间目标的空基/星载红外探测中的目标背景临边对比度问题进行物理建模,详细阐述对比度的定义和模型中的高层大气辐射问题.利用适于模拟高层大气辐射的非局域热平衡模式,结合探测器噪声假定,计算理想黑体目标的临边对比度并分析高层大气辐射特性对对比度的影响.模拟结果表明,在评估目标探测可行性时必须考虑探测器噪声的影响;在高层大气临边路径下水汽波段比大气窗区的可探测性更好,而目标本征辐射与大气临边吸收和背景辐射间的关系导致了对比度复杂的变化特征.

A physical model was established for studying near-space limb radiance contrast when the target is detected by space-borne infrared surveillance system. The definition of limb contrast and radiation issues of upper atmosphere of the model was described in detail. The target＇s limb contrasts were simulated and analyzed to showupper atmospheric radiation properties＇ effects to the target visibility based on non-local thermodynamics equilibrium atmospheric model and assumed detector＇s noise. The results indicate that the detector＇s noise must be considered for evaluating surveillance feasibility correctly. The contrast at the traditional waveband of the strong absorption by water vapor is better than the often-used ‘atmospheric windows＇ for the upper atmospheric limb detection. The complicated contrast characteristics result from the relationship among target inherent radiation,atmospheric absorption and background radiation.