In the survey reported here, an attempt has been made to identify 

 the kinds of transponders potentially available to enhance the perfor- 

 mance of various remote sensing techniques and to quantify the degree 

 of enhancement that is feasible. However, it should be noted, that the 

 state of the art in transponders and associated devices is advancing 

 rapidly--largely in response to advances in digital storage and processing 

 technology- -so that the potential for improved performance from such 

 devices is large. 



From the standpoint of their contribution to the performance of 

 functions important to fishing zone enforcement, the drawback of most 

 transponding devices is that cooperation on the part of the target fitted 

 with the transponder is required. That is, a transponder (beacon) 

 that simply enhances detection or supplies a preprogrammed identification 

 signal can operate independently of any input from the target. To supply 

 additional information, such as activity status, intentions, etc., re- 

 quires cooperative effort on the part of the target in the -form of manual 

 or automatic input of the information to be transponded. Thus, it is 

 much easier to devise an "intelligent transponder" than to insure that 

 it is reliably supplied with the information to be transponded. 



In this survey, we have called attention to the functional enhance- 

 ment that is technically possible through the use of various kinds of 

 transponders. However, consideration of how to insure that appropriate 

 information about the target is supplied to the transponder is beyond 

 the scope of the survey. 



D. Performance Enhancement Using Combinations of Sensors 



Experience in performing the detection and classification functions 

 associated with Navy and USCG ocean surveillance missions has shown that 

 maintaining an adequate "picture" of vessel (and aircraft) activity in 

 an ocean area requires inputs from a variety of sensors. For example, in 



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