The penetration depth of light in the sea is defined for remote sensing purposes as the depth above which 90% of the diffusely reflected irradiance (excluding specular reflectance) originates. It is demonstrated that for a homogeneous ocean, this is the depth at which the downwelling in-water irradiance falls to 1/e of its value at the surface. Penetration depths as a function of wavelength are presented for a variety of water types, and a mean penetration depth
for a broadband sensor is defined and applied to the MSS on ERTS-1. The maximum
expected for ERTS-1 is found to be somewhat less than 20 m.
© 1975 Optical Society of America
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