基于无源点阵的高分辨光学卫星传感器在轨定标方法研究

Calibration on-orbit is one of critical techniques for information quantification of optical remote sensing. And it is also significant to the application of high spatial resolution satellite remote sensing data and development of future satellite sensors. Considering the difficulties and low efficiency in deployment quickly and transportation, it can't meet the requirement of normalizable and high-precise calibration for high resolution satellite optical cameras based on the large area tarps. The research is intent to explore radiometric calibration and modulation transfer function estimation in-flight of high spatial resolution satellite optical cameras using point array by theory analysis and experimental verification. The quantitative relationship between point target signal and sensor's effective pixels response could be acquired through model analysis of an imaging system and radiant flux of the point. And the target reflectance measurement at site is accurately improved in laboratory. So the accuracy of radiometric calibration and MTF estimation on-orbit for high resolution sensors can be effectively enhanced.Therefore,it can achieve high-precision, high-frequency and normalizable mobile calibration applications for high spatial resolution satellite sensors based on the light weight and small cubage point array. The study would help to improve the calibration accuracy of optical satellite remote sensors and help to improve the information quantification level of optical remote sensing. And the study would also promote the technological progress for in-flight performance measurement of satellite sensors.

在轨定标是光学遥感信息定量化的关键技术之一，关系到高分辨卫星遥感数据的应用和未来卫星遥感器的发展。基于大面积人工靶标的定标方法在快速布设、运输转移等方面实施难度大、效率低，难以满足高分辨卫星相机常态化高精度定标的应用需求。本课题采用理论分析与试验验证相结合的方式，探讨基于无源点阵的高分辨光学卫星相机在轨辐射定标及MTF检测方法。通过成像系统模型分析及点辐射扩散研究，建立点目标信号与遥感器有效像元区响应值的定量关系；并将目标反射率的现场测量改进为实验室的精确测量，以有效提高高分辨遥感器在轨辐射定标及MTF检测的精度，进而为实现基于小型轻量化无源点阵目标的高分辨率遥感器在轨高精度、高频次、常态化的移动式定标应用提供理论依据。该研究不但能提高我国光学卫星在轨辐射定标及MTF检测精度，而且能提高我国光学遥感信息定量化水平，对推动我国遥感器在轨性能检测等技术进步方面也有重要价值。

在轨定标是遥感信息定量化的关键技术之一，辐射定标与MTF检测是高分辨光学卫星传感器成像质量评估的重要参数，关系到高分辨率光学卫星遥感数据的应用和未来卫星遥感器的发展。. 提出一种基于无源点阵的高分辨光学卫星传感器在轨辐射定标与MTF检测方法。基于点源目标的在轨MTF直接检测方法，从遥感影像计算得到成像系统的点扩散函数（PSF），进而获取系统MTF。同时根据成像关系对点光源图像数据，利用非线性方程优化求解的方式，得到被测光学卫星传感器成像系统的一维线扩散函数（LSF）值，进而验证了可近似用高斯模型来表征高分辨率光学卫星传感器的点扩散函数。. 基于点目标的在轨辐射定标新方法是将目标反射率的场地多点测量转换为实验室高精度检测，结合同步大气光学特性参数测量，通过简化的辐射传输计算获取星载遥感器的入瞳辐亮度；根据点源法在轨点扩展函数检测，有效分离目标反射辐射与程辐射、背景辐射，消除了对气溶胶散射特性的假设，并突破场地替代定标易受时空及天气条件的限制，能够在复杂环境条件下实现高分辨率光学卫星传感器高精度、高频次移动定标。. 利用研制的小型化、轻量化点光源对高分辨光学卫星传感器进行了在轨定标试验，初步的试验结果表明：基于无源点阵的光学卫星传感器在轨MTF检测结果与基于刃边靶标的在轨检测结果差异优于5%，基于反射点源的光学卫星传感器在轨绝对辐射定标不确定度优于3%，与基于大面积灰阶靶标的定标结果差异为3.02%，简化定标流程的同时提高了定标精度与效率，实现了基于小型轻量化无源点阵目标的高分辨遥感器在轨高精度、高频次、常态化的移动式定标。. 该项研究工作的开展不但提高了我国光学卫星在轨定标精度，而且提高了我国光学遥感信息的定量化水平，对推动我国光学遥感器在轨定标的技术进步有重要意义。