A moored optical buoy system has been developed by the National Space Development Agency of Japan (NASDA) for verification of ocean-observing remote sensing sensors of the Advanced Earth Observing Satellite (ADEOS). An underwater spectral radiometer was specifically designed for this optical system. The two upward radiance and downward irradiance correctors were connected with fiber optical system and were placed at the depth of 1.5 m and 6.5 m. The collector parts of the radiometer were extended from the center of the buoy system in order to avoid self shading with 3 m and 1.2 m arms at the depth of 1.5 m and 6.5 m, respectively. Spectral incident irradiance was measured at top of the buoy system. Phytoplankton pigment concentrations were monitored by Aquatracka-III fluorometer placed at the bottom of the surface float. Atmospheric temperature, pressure, humidity, wind speed and direction, water temperature at a depth of 1.2 m and 6.5 m, and wave height and direction were also monitored. In this paper, we present results from test deployment during January 16 to March 15, 1995, in the Suruga Bay, off Shizuoka, Japan, and compare the water-leaving radiance obtained by buoy with one observed by ship. The chlorophyll a concentrations calculated from water-leaving radiance were also compared with chlorophyll fluorescence measured by fluorometer. It was proved that the self shading and wind affected the radiance and irradiance in the sea. It becomes clear that the quality check of the buoy data is very important for verification of the satellite data. We present also the verification plan of atmospheric correction and phytoplankton pigment for ADEOS/ocean color and temperature scanner (OCTS) using the sea truth data obtained from this buoy system and ships.¿ 1997 American Geophysical Union