Abstract
The direct solar radiation observed by instruments aboard the ground-based solar tracking devices, is needed to estimate aerosol optical thickness. However, the instruments on unstable platforms such as ship sometimes don't accurately point the sun. In our research, the PAR radiometer that can observe direct solar radiation with high stability has been developed. The shadow band of the PAR radiometer assists to obtain stable observation data on any unstable platform. Actually the newer-developed PAR radiometer doesn't need tracking the sun anymore. We have also developed an algorithm that retrieves aerosol optical thickness from the PAR radiometer data. From the experiments performed from 2006 to 2008, aerosol optical thicknesses were estimated with high accuracy.
