ENVIRONMENTAL LIMITATIONS TO DEEP SEA SEARCH 



F. N. Spiess, J. D. Mudie, C. D. Lowenstein 



University of California, San Diego 

 Marine Hiysical Laboratory of tiie 

 Scripps Institution of Oceanography 

 San Diego, California 92152 



During the study conducted by the Deep Submergence Systems Re- 

 view Group in the aftermath of the THRESHER search it became clear that 

 acoustic, magnetic and optical search systems should be developed to en- 

 hance our ability to find objects on the deep sea floor. It was equally clear, 

 as we investigated hypothetical search systems, that we had no information 

 on which to estimate, even crudely, the limitations which natural roughness 

 of the deep sea floor would provide to the effectiveness of system operation. 

 This limitation might be either in raising the effective "noise" level at the 

 system output in a general way or might appear in terms of false targets. 



With support of ONR and DSSP we have brought into operation a 

 towed instrumentation system capable of observing pertinent fine scale 

 aspects of the deep sea floor and have begun an actual program of operation 

 at sea to determine these limitations . The system consists of an instru- 

 mented towed body which can be operated from a research ship, using an 

 appropriate towing wire to provide both electrical and mechanical connection 

 between the two. The observational systems which are operational at this 

 time are precision down-looking echo sounder, up-looking sounder, bottom 

 penetration sounder, side-looking sonar, camera and lights, and proton 

 magnetometer. Transducers for most of these can be seen in the picture of 

 the towed body (Fig. 1). High quality local navigation near the sea floor is 

 provided by an acoustic transponder system.—^ — ' All outgoing signals for 

 the acoustic systems as well as trigger signals for camera and magne- 

 tometer are transmitted from the ship down the coax core of the towing wire 

 and all acoustic and magnetometer signals are sent back up the same line. 



We have, in the past year, operated in several areas, four of 

 which are shown on the index map (Fig. 2). In three of these (shown by 

 circles) transponders were planted and an area of 80 to 120 square miles 



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