TIME VARIATIONS OF SOUND SPEED OVER 

 LONG PATHS IN THE OCEAN 



G. R. Hamilton 

 Ocean Science and Technology Division 

 Technology Division 



From 1961 to 1964 a series of precisely located and timed 

 SOFAR charges were fired off Antigua to measure the trans- 

 mission time stability of the sound channel axis arrival 

 (i.e., the SOFAR signal cutoff) to MILS hydrophones at 

 Eleuthera, Bermuda, the Canary Islands, Barbados, 

 Ascension and Fernando de Noronha. The sound transmission 

 speed was found to be stable for a few hours but it 

 could not be predicted a week in advance. An application 

 to the precise location of missile impacts using SOFAR 

 signals, based on the dropping of SOFAR charges at the 

 missile impact position within a few hours of missile 

 launch, is described. 



The most extensive measurement of sound-speed variations over 

 long distances were made in a program in the early 60 's called SCAVE, 

 for Sound-Channel Axis Velocity Experiment. The locations of the ex- 

 periment are shown in Figure 1. Results were published in the proceed- 

 ings of the Naval Underwater Acoustics Symposia in 1962, 1963, and 

 1964. 



The measurements were designed to make it possible to use SOFAR 

 charges to determine the accurate impact position of Polaris missiles 

 launched southeast into the Atlantic from Cape Kennedy, Florida. With 

 a range of about 1600 miles, these missiles impacted in the open ocean 

 east of the Caribbean. For this flight range, they could not be tar- 

 geted to impact close to an island or coast line where shore-mounted 

 radars or shore-connected bottom hydrophones could be used for deter- 

 mining impact position without overflying islands. Could SOFAR charges 

 carried in the missile be used to accurately locate the impact position 

 at a mid-ocean location? What impact position accuracy would SOFAR 

 charge provide? 



