In order to estimate chlorophyll-a concentration(Chl.a) for coastal lagoon environments using satellite optical sensor, simultaneous water quality surveys with satellite observation were conducted from July to November 2001 in Lake Shinji and Lake Nakaumi. Thermal infrared image of Terra/ASTER at night in August 2001, and a radar image of ERS 2/ SAR, a visible image of SPOT-2/HRV, and in-site water quality datasets in November 2001, were obtained. Comparison between the simulated ASTER data using spectral reflectance data obtained from the lakes on boat, and in-situ Chl.a was performed. Consequently, Band ratio of Band 1 and Band 2 or Band ratio of Band 1 and Band 3, and Logarithm of Chl.a had comparatively high correlation. It was suggested that Chl.a distribution in the lakes may be able to be estimated using ASTER data.