Stilwell 



analyze wavelengths approaching the size of the camera field of view. 

 The high frequency peak was beyond the camera resolution and does 

 not show. The low frequency spectral peaking is quite evident 

 in the region around 20 cm water wavelength. 



CONCLUSIONS 



.The small wave theory developed here should allow a useful 

 estimation of the spectrum of the ocean under the conditions of 

 clear or overcast sky^ camera depression angle about h^° , use of 

 a polarizing filter, multiple photographs to reveal directional 

 spectra and to obtain spectral smoothing, etc. The technique will 

 have to be compared with the spectra obtained by present installa- 

 tions but shoiild allow an extension of measurements into the 

 capillary wave region. It should be useful in studying the build- 

 up of wave systems (the transient spectral changes) and allow the 

 study of the turbulent structure and energy transfer properties 

 of the air-sea boundary layer. Although the technique is not 

 applicable in all circumstances for which sea clutter data is re- 

 quired, it should allow a tabulation of high frequency spectral 

 characteristics imder a wide range of local wind conditions which 

 would enable non-spectral measxxrements to yield a good estimate of 

 the actual sea conditions. 



REFERENCES 



1. C.A. Taylor and H. Lipson, "Optical Transforms," Cornell 

 University Press, Ithaca, N.Y., 1964. 



2. L.J. Cutrona, E.N. Leith, C.J. Palermo, and L.J. Porcello, 

 "Optical Processing and Filtering Systems," IRE Trans, on 

 Info Theory, June I96O. 



3. B. Kinsman, "Wind Waves: Their Generation and Propagation 



on the Ocean Surface," Prentice -Hall, Englewood Cliffs, N.J., 

 1965. 



179 



