to flow past it as the probe drops through the 

 water. This sensor is connected to the recorder 

 through a hard-wire link. The wire is com- 

 posed of three insulated conductors (Model T-3 

 probe), but it is very fine and has a breaking 

 strength of about 8 oz. (227 g.). As the 

 ship proceeds on course, a dual spooling 

 system allows the wire to pay out freely from 

 the canister in the launcher aboard ship while 

 simultaneously the wire is payed out freely 

 from the tail end of the ballistically shaped 

 and finned probe as it falls vertically through 

 the water. The temperature is recorded on the 

 analog recorder which has a modified balanc- 

 ing bridge circuit. The probe has a calibrated 

 rate of descent so that the depth is determined 

 by the time interval from entry into the water. 

 The recorder operates automatically. The 

 recording cycle starts when the probe enters 

 the water. After a period of recording the 

 temperature-depth analog trace, the cycle 

 stops and the recorder returns to a standby 

 condition. 



Figure 4. — Position of launcher in relation to hull near 

 vessel stern. For the purpose of the photograph the 

 launcher was moved to its alternate mount on the star- 

 board side at a location comparable to the portside 

 mount used during the trip. The deck is between 25 and 

 30 ft. (8 - 9 m.) above the waterline. 



The specifications of the system are as 

 follows: 



Temperature: 



Range: 28° to 95° F. (-2° . 



35° C.) 



Accuracy: +0.36° F. (±0.2° C.) 



Response time: 0.1 sec. 



Depth: 



Range: to 1,500 ft. 



(0 - 460 m.) 



Accuracy: ±15 ft. (4.6 m.) or 2 



percent of depth, 

 whichever is greater 



Time for deploy- 

 ment: 90 sec. 



Ship's speed: to 30 knots (0 - 15m. 



per second) 



NSRT (Near-Surface Reference 

 Temperature) Unit 



An NSRT unit is also being tested for accu- 

 racy and reliability during this project. The 

 device is intended for use on merchant ships 

 so that sea temperatures will not be read from 

 mercury-in-glass thermometers in the intake 

 system. The system consists of a thermistor 

 probe installed in the ship's sea-water intake 

 and a remote temperature-indicating meter. 

 On the SS CALIFORNIAN the meter was in- 

 stalled near the XBT recorder so that the 

 temperatures could be used as a subsurface 

 (26 - 30 ft. or 8 - 9 m.) check against the 

 XBT temperatures. Usually the meter would 

 be installed on the bridge where the weather 

 report is logged. The NSRT has an accuracy 



of ±0.15° C. over a total range of -2° C. to 

 40° C; it uses four 12-degree overlapping 

 scales. 



Installations Aboard SS CALIFORNIAN 



Aboard the SS CALIFORNIAN the launcher 

 for the XBT system is mounted on the port 

 rail of the main deck about 25 ft. (7.5 m.) 

 from the stern. This is slightly aft of the point 

 where the hull of the vessel begins to curve 

 inward toward the stern so that the wire trails 

 aft with little danger of contact against the 

 side of the ship (fig. 4). The probe enters the 

 water a few feet ahead of the wake. The XBT 

 recorder and the NSRT indicator are installed 

 one deck below the launcher in an area adjacent 

 to the boatswain's locker. The distance from 

 the XBT launcher to the recorder is about 45 

 ft. (14 m.). The distance from the NSRT sensor 

 in the engineroom to the indicator aft is about 

 200 ft. (60 m.). The intake for the sea-water 

 line in which the NSRT sensor is mounted is 

 about 25 to 28 ft. (7-8 m.) below the surface, 

 depending upon vessel loading. 



OBSERVATIONS 



The locations of the observations on the 

 outbound leg from San Francisco to Honolulu 

 are shown in figure 5. Numbers are not con- 

 secutive because all probe releases were num- 

 bered serially whether they were successful 

 drops or failures. The XBT drops on the out- 

 bound leg were made by the senior author, and 

 uneven spacing occurred while he was becom- 

 ing familiar with the system and establishing 

 a routine convenient for ship's personnel. 

 Licensed officers of the SS CALIFORNIAN 

 made most of the observations on the return 



