tern. Success with this procedure was 

 often thwarted by the current. As CUB- 

 MARINE increased the diameter of 

 her circling pattern, she was pushed 

 continually down current, so that the 

 ground track of the spiral search pat- 

 tern became corkscrew shaped. The 

 pilot was unable to correct for this, as 

 he had no navigation system, and visi- 

 bility was too poor to allow him to 

 visually fix a spot on which to circle. 

 If the spiral search failed to locate the 

 target, another sonar vectoring at- 

 tempt was made. 



Plotting the track of CUBMARIISE's 

 progress was an especially frustrating 

 problem. A continuous plot of the 

 MSO's track was maintained using 

 Decca Hi^Fix andlor range and bear- 

 ing fixes from landmarks on shore. 

 CUBMARII\E's position was then plot- 

 ted relative to the known position of 

 the MSO. Two procedures were em- 

 ployed simultaneously in the plotting 

 of CUBMARINE's position. The pri- 

 mary system was for sonar to deter- 

 mine the relative range anil bearing of 

 the submarine from the MSO. This 

 method was subject to the inherent 

 inaccuracies of the soniir, and was 

 also largely dependent on the profi- 

 ciency of the sonar operator. Keeping 

 sonar contact with both the target and 

 the submarine was often a difficult 

 task for the sonar man. As he adjusted 

 the focus of one he could easily lose 

 contact with the other.'''' 



In the same report Barringer notes that 

 this system was replaced by the marker 

 buoy, the adequacy of which has been de- 

 scribed. 



Pinger (Sub)-Hydrophone (Surf): 



One of the earher approaches to tracking 

 was by the attachment of a pinger to the 

 submersible and a baffled hydrophone to the 

 surface ship. As the submersible's ping was 

 received by the support ship it would orient 

 the hydrophone until the loudest ping was 

 obtained, and froin the direction in which the 

 receiving element was pointing, the relative 

 bearing of the submersible was obtained. 

 Slant range, on the other hand, was ob- 



tained from the submersible's UQC. In some 

 instances the hydrophone was lowered di- 

 rectly from the support ship; in others, it was 

 lowered from a small boat. The latter ap- 

 proach introduces a new set of errors, be- 

 cause now the range and bearing from sup- 

 port ship to small boat must be obtained 

 before the relative slant range and bearing 

 to the submersible can be calculated. Figure 

 10.16 diagrams the tracking procedures for 

 STAR III and DS^OOO, the origin of the 

 ship-to-small-boat error is apparent. 



PoUio (21) describes this tracking system 

 as follows: A 20-kHz pinger on the submers- 

 ible was tracked from the small boat by a 

 baffled hydrophone oriented to obtain the 

 loudest ping. The hydrophone angle to the 

 submersible was estimated, and the heading 

 of the small boat was obtained from an "au- 

 tomobile-type" compass. Slant range from 

 small boat to submersible was found through 

 the underwater telephone and a stopwatch 

 with a verbal "Stand-by-Mark" command 

 from the surface. Range and bearing to the 

 small boat from the support ship was esti- 

 mated. PoUio estimates at least a 400-yard 

 horizontal position error for the submersible 

 relative to the support ship. 



A variety of pinger frequencies can be and 

 has been used {e.g., 20, 27, 37 kHz), and in the 

 early dives of ALVIN (and others as well) the 

 8-kHz underwater telephone was set on CW 

 transmission. This continuous wave signal was 

 received by a trainable line-hydrophone for 

 bearing. A further modification to ALVIlTs 

 telephone provided transponder range on the 

 surface ship's telephone. According to Rainnie 

 (19) this system gave an estimated position ac- 

 curacy of the submersible relative to the sup- 

 port craft of ±380 yards (1,140 ft) at 6,000 feet in 

 depth. 



The shallower such systems are used, the 

 better the accuracy, but for precise survey- 

 ing they are of little value. Repeatability is 

 another area that suffers, and the following 

 account of a current meter array recovery by 

 ALVMIISAUT provides an excellent, if not 

 classic, example of the inadequacies, frustra- 

 tions and ingenuity of early tracking sys- 

 tems, submersibles and crew, respectively. 

 (Chapter 11 describes the salvage equipment 

 used in this retrieval and is referred to for 

 further details.) 



498 



