Mapping optical parameters of coastal sea waters using the Hyperion imaging spectrometer

The Hyperion instrument on-board the EO1 satellite is an imaging spectrometer capable of acquiring hyperspectral data with over 200 contiguous spectral bands of about 10 nm bandwidth. The instrument is not designed for ocean observation. Nevertheless, case 2 water near the coastal regions with high sediment loading usually has higher reflectance in the visible wavelength region than the clear case 1 water in the open oceans. Hence, the signal-to-noise ratio of Hyperion data over coastal waters may be sufficiently high, such that meaningful measurements of the optical properties of the coastal sea waters are possible. We tested the use of Hyperion imagery in retrieving and mapping the distributions of the coastal sea water optical parameters in the Singapore Strait. The Hyperion reflectance spectra were fitted to a coupled sea water reflectance and atmospheric transmission model. The water reflectance corrected for atmospheric effects could be computed from the fitting parameters. This method of inverse modeling by spectral fitting was able to separate the confounding effects due to scattering by suspended sediments and absorption by chlorophyll and dissolved organic matter. Spatial distributions of these three main constituents of coastal waters could be obtained.