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

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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