星载激光测高仪多模式回波是由多个目标产生的子脉冲组合而成。根据多模式目标的空间分布特点, 采用倾斜角、区域面积、中心位置和高度等参数实现其子目标的几何化建模, 结合目标响应函数的基本定义, 利用线积分的方式构建了子目标响应函数的表达形式。同时, 基于一阶矩理论推导出子目标激光测距真值及其修正值的数学模型。以星载激光测高仪GLAS系统参数为输入, 利用数值分析的方法, 模拟出子目标倾斜角、面积和位置对接收脉冲回波形态和激光测距修正值的影响。结果表明, 随着子目标倾斜角、区域面积和子目标偏离光斑中心距离的增加, 激光测距修正值也逐渐增大。针对平坦目标、缓坡目标和陡坡目标, 其激光测距修正值分别达到1.33 m、4.98 m和12.07 m, 其影响程度非常大。基于激光测距修正值的分布规律, 以子目标倾斜角、面积和中心偏距为变量, 采用线性函数描述了激光测距修正值的理论表达形式, 所得结论对于提升多模式激光测距值的测量精度具有重要的指导作用。

Satellite Laser Altimeter multiple mode waveforms are composed of sub-pulses generated from several targets. According to the spatial distribution characteristics of multiple mode targets, the geometric modeling of the sub-target was realized by using the parameters such as the slope angle, the area, the center position and the height. Combined with the basic definition of the target response function, the expression of the sub-target response function was built up by using the line integral method. Meanwhile, the mathematical models of laser ranging and its corrected value for sub-target were derived on the basis of the first order moment theory. Using some parameters of Geoscience Laser Altimeter System(GLAS) as input, the influence of slope angle, area and the center position on the shape of received pulse waveforms and the corrected value of laser ranging was simulated by numerical simulation method. The results show that the corrected value of laser ranging becomes larger with the increase of the slope angle, the area and the center position of sub-target. As for the sub-target with low relief, moderate relief and high relief, the corrected value of laser ranging can be reached at 1.33 m, 4.98 m and 12.07 m, respectively, which exerts a tremendous influence. In term of the regularities distribution of the corrected value of laser ranging, its theoretical expression is described with linear functions by using slope angle, area and the center deviation distance as variables. The conclusion has important guiding effect for the improvement of laser ranging accuracy for multiple mode targets.