TM No. 306 



After the surface float was launched^, the specified amount of wire 

 was payed-out through an indicating meter wheel while the vessel steamed 

 slowly up wind. When the proper amount of wire was payed-out, the cheek 

 clamp (Figure 5C) was attached to the suspension wire. The parachute 

 and a 50-pound weight were also secured to the cheek clamp (see Figure k) 

 and the suspension wire was cut. The weight was then lowered over the 

 side until the parachute shrouds carried the full weight. At this time 

 the weight was released and the parachute was pulled downward by the 

 weight. (The parachute is payed-out in the reverse manner to that of 

 a parachute in the air i.e., the shrouds are payed out first, the canopy 

 being the last to enter the water.) In all cases, it was possible to 

 see the parachute open under water. 



All of the drogues used during this program were identical in 

 construction. 



NAVIGATION AND TRACKING 



The positions of the surface-floats relative to known landmarks 

 were determined with the Decca Hi-Fix System (Decca Navigator System, 

 Ltd., London), and an auxiliary fix was taken with navigation radar. 



The H.J.W. FAY was equipped with a Decca kOk- navigation radar 

 which was specified to have a frequency of 9320-9^80 mc/s and a display 

 discrimination of 20 yards. On shorter range scales (range scales in 

 nautical miles are O.75, I.5, 3, 6, 12, 2k, k8) , the range ring accuracy 

 is 1^ percent of the maximum of the range used or 75 yards, whichever 

 is the greater. The variable range marker accuracy is better than 

 1 percent of the range ring accuracy. The bearing resolution is +_1° 

 (Ref.2). The OCEAN PEARL was equipped with a Decca 303 Navigation 

 Radar which has characteristics similar to the Decca kOk aboard the 

 H.J.W. FAY. The ranges most used were 6, 12, and 2k nautical miles. 

 The Decca Hi-Fix is a high precision, lightweight, electronic position- 

 fixing system, intended primarily for use at short ranges. The system 

 is designed for hydrographic, geophysical, and other surveys in which 

 an accuracy of less thaji one meter is required, and which demand the 

 use of an electronic surveying system that is readily portable, simple 

 to operate, and quick to install. Decca Hi-Fix receivers were 

 temporarily installed on both vessels, and were used independently 

 but in conjunction with the radars. The principle of the Hi-Fix 

 can be described in the following manner. A set of stationary, 

 standing electromagnetic, wave patterns are generated by radio 

 transmitting stations. These patterns form coordinates in terms of 

 which a radio receiver (carried by the user) provides continuous 

 indication of its position with respect to the transmitting stations. 

 If the positions of the statioiB are known, the signal received by the 

 receiver may be converted into geographical coordinates by reference to 

 a transformation chart. Computers can also be used for this conversion . (Ref .3) 



