independently or in combination for CURV IV: (1) a pulse positioning 

 measurement system, (2) a phase -comparison system, and (3) a phase 

 correlation system. 



NUC's approach to overcoming the technical barrier will be to 

 evaluate the short base-line system and to develop a system based 

 upon this evaluation. The system will be used at 20, 000 feet and 

 tested at-sea with CURV III, 



Precision Bottom Navigation 



Precision bottom navigation is knowing the position of the vehicle 

 with respect to the bottom accurately enough to enable the vehicle to do a 

 systematic small area search or to enable the vehicle to return repeatedly 

 to a work site. The accuracy needed is estimated to be approximately ±20 

 feet. At the 20,000-foot depths, this represents an accuracy of 0.1%. 



CURV II has used its sonar and compass in conjunction with a bottom 

 beacon to accomplish some small area searches. This technique is time 

 consuming (sonar range is only 300 feet) and accuracies of only about ±50 

 feet are obtained. 



A long base line system looks promising in overcoming this technical 

 barrier. Long base line systems are currently in use but not in a CURV 

 application^ and CURV operations present some unique problems: 

 (1) CURV has to operate on the bottom thereby decreasing the effective 

 range of the bottom beacons and magnifying the interference due to bottom 

 terrain, and (2) the CURV vehicle generates acoustic noise which could 

 interfere with the long base line systems operation. In overcoming this 

 technical barrier, navigation systems will be studied for application to 

 CURV operations, navigation equipment will be modified and evaluated, 

 the acoustic noise interference will be defined, and development approaches 

 delineated. 



CONCLUSION 



It should be reiterated that the type of problems which appear 

 pre-eminent now are based on assumptions that certain CURV 

 techniques and equipment will suffice or fail. Much of the initial 

 CURV IV development work will be to define the exact performance 

 at 20, 000 feet of CURV III components, which could alter the 



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