and reverberation, the Advanced Research Projects Agency of the 

 Department of Defense is sponsoring an effort at the Woods Hole 

 Oceanographic Institution to improve manned submersible 

 navigation by bounding sound signals off the ocean surface and 

 hence over the intervening ridge. 



In another research effort, the Naval Undersea Center is 

 developing computerized integration and display techniques for the 

 visual representation of acoustic signals. These techniques will 

 present the submersible operator with a geographically oriented 

 navigational picture. It is expected that by 1975 these techniques, 

 combined with the surface-bounce navigation system, will be 

 utilized on the RUWS and the Alvin. 



Productive utilization of deep submersible vehicles requires 

 operations in waters of low visibility and high turbidity where 

 optical systems are severely constrained. Improved optical systems 

 result in only slight gains in such environments. To overcome this 

 critical operational constraint, a real-time, high-resolution acoustic 

 imaging system is being developed under contract. This system, 

 utilizing acoustic holography with computer reconstruction of the 

 image, will provide a distinct image to 100 feet. It will be constructed 

 for installation on the Navy submersibles Sea Cliff and Turtle. 

 Delivery of the system is expected in January 1974. All three acoustic 

 navigation systems could be used on civilian-operated undersea 

 vehicles such as those for monitoring or repairing underwater oil 

 rigs, or by submarine oil carriers which have been suggested for ice- 

 covered waters. 



Research to Support Diver Operations 



To provide knowledge and safety guidelines to benefit the diver, 

 work is underway on a new civilian diving manual, the collection of 

 data on the effects of shorter decompression after saturation diving, 

 and on long-term health problems resulting from exposure to 

 underwater pressure. The development of a civilian diving manual, 

 being prepared by NOAA primarily for scientific and working 

 divers on NOAA-sponsored projects, will be completed in mid-1973. 

 Data from the U.S. Navy, universities, and industry are being 

 reviewed and integrated into the manual wherever applicable. 



A NOAA effort is examining new safe vertical excursion limits for 

 divers saturated at various depths with nitrogen-oxygen breathing 

 mixtures. This research promises to open new vertical depth range 

 capabilities without increased decompression to permit more 

 flexible diving from ocean floor laboratories on the continental shelf. 

 Vertical excursions with no decompression, simulated in hyperbaric 

 chamber tests, have thus far been free of decompression sickness 

 and nitrogen narcosis at greater depths and for longer durations than 

 previously thought possible on nitrogen-oxygen breathing mixtures. 



The Navy has applied acoustic technology in its Doppler bubble 



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