cipal, doppler measurements could therefore yield inde- 

 pendent estimates of, say, the mean wave height and mean 

 period of the sea. However, apart from the aforementioned 

 difficulties in resolving wave-induced doppler shifts 

 from satellites, the theoretical predictions must be 

 regarded as qualitative until the hydrodynamic interactions, 

 which are generally of order comparable with the electro- 

 magnetic interactions, are Incorporated in the model. This 

 would not only be useful for the interpretation of the 

 doppler spectra, but may also enhance the value of cross- 

 section data by the prediction of new types of signatures 

 (such as the upwind/downwind asymmetry, cf. [24]), which may 

 be more readily distinguishable from the unmodulated Bragg 

 return than the modifications induced by electromagnetic 

 interactions alone. 



Perhaps the strongest argument for developing a 

 quantitative wave-facet interaction model including both 

 types of interaction is the recent Interesting proposal to 

 determine the complete wind-sea spectrum by means of 

 sinusoidally modulated microwaves (Ruck et al , (1972) — 

 a similar suggestion was made also in an earlier unpub- 

 lished communication by W.S. Ament ). The power emitted 

 by a microwave beam consisting of the superposition of two 

 monochromatic waves with closely neighboring frequencies 

 and horizontal wavenumbers ( cu , k ) and ( w , k ) , 



1 ~ 1 2 ~2 



25-40 



