Although the state of the art must be significantly improved 

 for both tides and tsunamis, it appears that tides are more 

 likely to be successfully studied from space in the fore- 

 seeable future. 



1. INTRODUCTION 



Inasmuch as both tides and tsunamis are shallow water 

 waves (wave length much greater than water depth), there 

 may be a tendency to assume that there is an equal potential 

 for monitoring these from space. However, this does not 

 follow because there are significant differences in the 

 physics of these phenomena. Accordingly, some considera- 

 tion of each is necessary for arriving at an evaluation of 

 the potential for monitoring from spacecraft, 



2. TIDES 



There are some distinctive features that differentiate 

 tides from most, if not all, other geophysical phenomena. 

 An energy spectrum for most parameters is a continuum which 

 peaks in one or more frequency bands; tides have a line 

 structure and the frequencies of the lines are very accurate- 

 ly determined from astronomical data. The phases for each 

 of these lines are locked into astronomical events and the 

 signal to noise ratio is usually very high. Finally, it 

 can be assumed that the Q of the ocean response to tide- 



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