A TOWED NEAR-SURFACE OPTICAL REFLECTANCE METER FOR MEASURING OCEAN COLOR IN SUPPORT OF REMOTE-SENSING

An underwater optical instrument, the Lightfish, measures near-surface irradiance reflectance in six spectral channels while it is towed fro m a research vessel at a depth of a few metres. The detectors are conf igured such that all downward-looking detectors observe the same instr ument shadow. Effects of self-shading are negligible for waters and wa velengths having absorption coefficients less than 0.3 m(-1). Variance in the derived spectral reflectance ratios is shown to be significant ly reduced compared with that in single channel irradiance measurement s. The instrument can be used to develop remote sensing algorithms as well as for other oceanographic applications.