The remote sensing of ocean color by satellite is a useful technology for identifying water constituents which is highly repeatable, rapid, and covers a wide range. However, difficulties arise when we apply it to coastal waters due, for instance, to their optically complex constituents and low spatial resolution. In particular, the backward scattering coefficient, which governs the ocean color together with the absorption coefficient, is extremely difficult to measure. Recently, we developed a

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... ypass method to determine the backward scattering coefficient with an accuracy of 3 %. This method can help us to develop an ocean color algorithm for coastal waters. We also developed a multi-band imaging radiometer, which is compact and light weight and can be mounted on a multicopter. Our radiometer has 12 channels at wavelengths between 400 nm and 800 nm, and the signal-to-noise ratios of all channels can be adjusted to almost the same level with the help of neutral density filters. We made several test flights to check the performance of the radiometer in Suruga Bay. Although we only performed a simple analysis, the results showed that: 1) we could clearly detect high-density particle areas; 2) the influence of the atmosphere on the radiance measurements is negligible in the case of low-latitude observation; and 3) the observed spectral radiance exhibited the typical spectral shapes of Case2 Water.