地球温暖化指標の測定精度向上を目的とした地球観測衛星の校正技術開発

众所周知，对地观测卫星上安装的光学传感器的输出信号在轨道上表现为衰减。降解的一个最可能的原因被认为是污染效应。由于污染的存在，即使是极微小的水平，也会影响光学传感器的性能，因此有效的污染控制对地球观测任务的成功至关重要。本研究提出建立污染效应基础数据库，从理论和实验两个方面对污染效应进行认识。对于微粒污染，进行了以下分析1。利用EPMA对在种子岛航天中心卫星储存条件下采集的颗粒样品进行化学成分分析。结果表明，污染颗粒物的主要来源是人为污染。作为污染控制的第一步，测量了面积覆盖与表面清洁度之间的相关性。结果表明，卫星存储条件下光学表面的面积覆盖与实验室测量结果吻合较好。利用多探测器半球面光学散射仪测量了不同表面清洁度样品的双向反射分布函数（BRDFs）。通过数值计算发现，实验结果可以用Mie散射模型来解释。并对人为颗粒引起的brdf进行了测量。采用人工胶原蛋白作为试验颗粒样品。为了估计轨道上发生的粒子消除率，测量了由离心力或冲击引起的光学表面消除粒子的比例。结果表明，镜面旋转对面积覆盖百分比的影响不超过0.18%。对于分子污染，如果污染物的强吸收带存在于我们感兴趣的区域，则会严重影响传感器的性能。由于分子污染物有自己的吸收带，为了研究气态污染物的吸附量与光学透过率之间的关系，进行了以下分析：我们建立了基于体积法的测量系统。在0.3um<λ<20um范围内测量了光学材料透过率的变化。研究发现，N_2、O_2、CO_2等分子气体的沉积会改变光学材料中羟基的吸收谱。少

As is known that output signals of optical sensors equipped on earth observation satellites show the degradation on orbit. One of the most probable cause of the degradation is thought to be contamination effect. Since the presence of contamination, even in miniscule level, can affect the performance of optical sensors, effective contamination control is essential for the success of earth observation missions. In this study, it was proposed to create essential database about contamination effects and comprehend the contamination effects from both sides of theory and experiment.As for particulate contamination, following analyses were performed.1.The chemical composition analysis was carried out for the particulate samples collected under satellite storage condition at Tanegashima Space Center by EPMA. It was found that the major part of contaminated particles was man-caused.2.The measurements about the correlation between the area coverage and the surface cleanliness level were performe … More d as the first step of the contamination control. It was found that area coverage of optical surfaces put under satellite storage condition was well agreed with the results measured in laboratory.3.The measurement of bi-directional reflectance distribution functions(BRDFs) was performed for the samples with different surface cleanliness levels using the multidetector hemispherical optical scattering instrument. It was found that the experiment results could be explained by Mie scatter model from the numerical computation.4.It was also performed the measurement of BRDFs caused by man-caused particles. Artificial collagen was adopted as test particulate sample.5.In order to estimate the rate of particle elimination occurred on orbit, the fractions of eliminated particles from optical surfaces caused by centrifugal force or impact shock were measured. It was found that the variation of the percent area coverage owing to the mirror rotation was not more than 0.18%.As for molecular contamination, sensor performances would be affected seriously if the strong absorption bands of the contaminants exist in the region of our interest. Since molecular contaminants have their own absorption bands, In order to investigate the relation between adsorption quantity of gaseous contaminants and optical transmittance, following analyses were carried out.6.We built up the measurement system based on the volumetric method.7.The variations of transmittance of optical materials were measured within the range of 0.3um<λ<20um. It was detected that absorption profiles of hydroxyl contained in optical materials was changed by deposition of molecular gas such as N_2,O_2, and CO_2. Less