UNDERSEA TECHNOLOGY 



63 



TRANSPONDER 

 INTERROGATOR 



800-W FLOOD LIGHT 

 SHORT RANGE SONAR 



DIRECTIONAL HYDROPHONE 

 250-W FLOOD LIGHT 



HORIZONTAL OBSTACLE- 

 AVOIDANCE - SONAR 



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//DOPPLER NAVIGATION 



SONAR y, 



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MANIPULATOR 

 MATING SKIRT 

 (T-V CAMERA LIGHT, 



DEWATERING EQUIPMENT) 



Deep Submergence Rescue Vehicle (DSRV) sensor, navigation, and control equip- 

 ment locations. Many of these systems will be incorporated into the DSSV, which 

 is presently in the planning stage. 



measurements from two or more transponders. Replies from several trans- 

 ponders are distinguished by either different interrogation or reply fre- 

 quencies. 



A typical navigation transponder when released by the DSRV would 

 drop to the sea floor, and a float would lift the acoustic transducer about 

 300 ft above the bottom. The float is designed as a maximum buoyancy, 

 minimum drag body to limit the watch circle (uncertainty) in float loca- 

 tion caused by the ocean current. 



One of the limitations on range measurement arises from the bending 

 of sound rays. In deep water, especially at depths greater than 6000 ft, 

 sound signals are refracted upward. As a result, a shadow of the bottom 

 masks signals from navigational transponders at ranges greater than two to 

 three miles for submersibles operating in the vicinity of the bottom. 



Multipath interference causes another problem. Beacon returns usually 

 include both the direct sound rays and rays reflected off the bottom. 

 Since a typical beacon pulse width is 4 millisec, the reflected signal is only 

 slightly delayed, and thus comes in almost simultaneously with the trans- 

 mitted signal. This action can cause fading or complete cancellation of the 



