4. The present expendable bathythermograph is adequate for current 

 tactical needs in determining the sound velocity profile in deep water. 

 A possible problem area which, however, does not often occur in the 



deep ocean is the case of a nearly isothermal surface duct where salinity 

 data may be necessary to determine the velocity gradient. The development 

 of the surface vessel launched X.B.T. is complete. 



5. A study should be made of the adequacy of temperature data 

 alone to indicate the presence of a surface duct in shallow water where 

 sharp discontinuities in salinity can occur. The study should indicate 

 what advantage might be gained by the use of expendable velocimeters or 

 conductivity probes if such were available. The study should include 

 possible errors in the pressure correction term due to sharp changes in 

 density which will be common to all expendable instrumentation. 



6. Dependent on the results of the study (5.) a development program 

 should be aimed at producing an inexpensive expendable velocimeter and/or 

 conductivity probe, not to compete with the X.B.T. , but to supplement 



it for use in areas where temperature data might not suffice. There have 

 been several attempts at and suggestions of designs. The program need not 

 necessarily first compete with the current price of the X.B.T., but rather 

 should aim at producing an accurate instrument at a cost of perhaps $100 to 

 $200. If such an instrument were successful the decrease in cost for large 

 scale production could be predicted. 



52 



artbur ZD/iUttlc.ilm 



