application. Finally, a comparative summary is presented that identifies 

 the key performance and cost factors for each sensor technique analyzed, 



1. Microwave Radar Techniques 



a. Description 



Microwave radars have been used for ocean surveillance 

 in aircraft and ships for almost 40 years. The technology is highly 

 developed and the design principles are so well known that it is possible 

 to predict with high confidence the performance of any given design. 

 The remote sensing principle involved is simplicity itself. Pulses of 

 microwave energy are transmitted by a directional antenna and reflected 

 by any material objects it encounters. The reflected energy is subsequently 

 received and analyzed to determine the position and characteristics of 

 the reflecting objects. The direction of objects thus detected are 

 correlated with the antenna beam and their range determined by measuring 

 the time delay from pulse transmission to reception. The design problems 

 in building a radar for a particular purpose are to select a frequency, 

 power output, and pulse characteristics suitable for the detection of 

 desired objects at required distances and to determine optimal antenna 

 beam patterns and scanning methods to enhance the detection of desired 

 objects while minimizing interference by energy reflected from undesired 

 objects (such as the background). Beyond these fundamental objectives, 

 designers attempt to optimize designs in the cost-performance sense and 

 to devise methods of extracting more information about the character- 

 istics of detected objects and minimize the masking effects of background 

 clutter through processing of their radar returns, manipulating the 

 transmitted pulse characteristics, and optimizing antenna beam shapes. 



The basic information provided by a microwave radar 

 sensor relative to ocean surveillance is: 



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