strongly influenced by the wave field, but the passive 

 emission problem is rather analagous to the scattering case 

 in the sense that similar interaction models are applicable 

 in both instances. 



Space measurements of sea surface backscatter are best 

 made in the cm-dm wavelength band in order to combine good 

 beam resolution with weak transmission losses in the atmos- 

 phere. Synoptic coverage of the sea surface over distances 

 extending to several thousand kilometers can also be achieved 

 with land stations using decameter waves reflected from the 

 ionosphere. It has been shown that at these wavelengths the 

 higher-order doppler side bands of the sea echo can be 

 related theoretically to the one-dimensional frequency spec- 

 trum of the wave field ([23] [25] [8]). The interactions in 

 this case involve relatively long wind waves and are reason- 

 ably well understood. However, we restrict ourselves here 

 to microwave techniques applicable to satellites; unfortun- 

 ately, these are governed by interactions in the less 

 studied and dynamically more complicated high wavenumber 

 region of the surface wave spectrum. 



The backscattered return from pulsed microwave emission 

 contains statistical amplitude, phase and travel time infor- 

 mation, which can be largely summarized in terms of the 

 second moments of the signal. In the particular case that 

 the process is Gaussian, these provide a complete statisti- 



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