done with color photography over the ocean from satellite altitudes, we 

 do not know. If this is the case, its usefulness will be limited to 

 aoplications close to shore or in shallow water. Only soectroscopic 

 methods would then be of value in mappinq water color in deeper water. 



Light irradiatina the sea surface undergoes reflection and refraction. 

 The reflected portion is polarized in the usual way, that is, the component 

 of the electric vector parallel to the sea surface predominates in the 

 reflected light and, at Brewster's angle, is virtually the only component 

 present. This can be made use of to select either the reflected skylight 

 or the backscattered sunlight unwelling through the water surface, 

 depending on whether the desired information relates to the shape of the 

 reflecting surface or to the optical properties of the bulk water. The 

 refracted portion penetrates the sea and, in the absence of scattering, is 

 eventually extinguished by absorption. In reality, the light is scattered 

 by particles of all sizes, from molecules through the larger colloidal 

 particles and up to large bubbles or, in shallov; water, by the bottom. On 

 the high seas, about 5 percent of the incident light is backscattered upward 

 toward the sky. This is about equal to the skylight reflected at near- 

 incident angles and severalfold larger than the fraction of reflected 

 light passing throuah a suitably oriented polarizing filter. 



The backscattered light so recovered, having been subjected to 

 absorption and spectral scattering along a path length that varies with 

 the distribution of scatterers in the sea, is markedly different in color 

 from the incident "white" light. In clearest ocean water, the effective 

 path length is quite long and the upward scattered light is strongly blue, 

 with a dominant wavelength of 'lOOO A and a quite pronounced saturation or 



8-5 



