NATIONAL OCEANOGRAPHIC DATA CENTER 

 BATHYTHERMOGRAPH LOG 



ENVIRONMENTAl DATA 





RADIO MESSAGE INFORMATION 



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Figure C-6. Bathythermograph Log with slide inset 



Step 6. Lowering the BT. — After the sea sur- 

 face reference temperature has been taken the 

 BT can be lowered. The operator should pro- 

 vide himself with a round stick about 15 inches 

 long to be used to control the speed of the drum. 

 The following instructions apply to underway 

 lowering : 



CHECK THE DEPTH OF WATER JUST 

 BEFORE MAKING EACH LOWERING. 



Release the brake, and allow the wire to pay 

 out freely. Success in reaching the maximum 

 desired depth depends on paying out the wire 

 as quickly as possible. 



Watch the wire and the drum carefully, and 

 gently slow the drum with the stick if excessive 

 slack appears. Do not apply too much pressure 

 to the drum with the stick. Once the diving 

 motion of the BT is arrested it will not dive 

 deeper regardless of the amount of wire payed 

 out. 



The proper amount of wire to be payed out 

 will depend upon the speed of the ship, the type 

 of BT, whether or not the nose sleeve is attached, 

 and operator experience. Several lowerings 

 should be made to obtain ship-speed/wire-out 

 ratio for BT used. 



Stop the winch when the counter indicates 

 the proper length of wire has been payed out. 

 Apply the brake smoothly ; avoid excessive jerk, 

 it may part the wire. NOTE: Never pay out 

 the last layer of wire on the drum. 



Step 7. Retrieving BT. — As soon as the brake 

 is applied, the BT will stop diving and return 

 to the surface far astern. 



Haul in the BT at full speed. 



Guide the wire back and forth in even layers 

 on the drum. If the winch does not have a level 

 wind, use the wooden stick for proper spooling. 



Decrease the winch speed when BT is close 

 astern. Continue to haul in until BT begins to 

 porpoise (breaking clear of the surface and 

 swinging forward as the ship rolls or as wave 

 crests pass). NOTE: This the most critical 



C-4 



