Abstract
It is known that suspended particles accrete on surfaces of a satellite through its assembly, check, and storage phases. Particulate contaminants cause masking and scattering of incident light at optical surfaces and lead to the degradation of radiometric accuracy of optical sensors. Especially in the visual and infrared wavelengths, optical characteristics of the sensor is largely affected with the particulate contamination since the size of suspended particles are as large as the observational wavelengths. However, we have not had enough information about the influence of particulate contamination in the visual and infrared range. In this study, we measured the correlation between the area coverage and the surface cleanliness level as the first step of the contamination control. We adopted JIS powder sample as contaminants and measured the number and the area coverage of contaminants by a scanning laser microscope. The area coverage was measured in the range of the cleanliness level from 200 to 1, 000 and against two kinds of particle size distributions. It was found that cleanliness level 350 corresponded to 0.1% area coverage and 550 to 1%. Moreover, it was found that the area coverage might be changed by about three times owing to the difference of particle size distributions. We also compared the area coverages of particular contamination monitors set in the 2nd satellite assembly building at Tanegashima Space Center with our results from the laboratory experiments and found that both results were almost the same and the particle size of 15, um made the largest contribution to the area coverage.
