E-13 

 depletion of power. The cure in hindsight would have 

 been simply to stock a larger supply of fresh batteries, 

 perhaps of a different nature. 



Another problem encountered in deploying the camera sled 

 was the failure of the transponder navigation system. The 

 Interocean Acoustic Transponders and Releases intended for our 

 use were delivered too late to be adequately tested prior to 

 our field program. Unfortunately, during the first leg (E-2A-79) 

 of the cruise, we found that the acoustic release mechanism 

 was faulty. After several shipboard dry runs we made an attempt 

 at a sea trial. The release mechanism of the test transponder 

 failed to work, and the transponder was lost. In order to 

 retrieve it, we deployed a CTFM transducer at the site to find 

 the transponder during future submersible operations. Although 

 the transponder was sighted during this program, technical 

 difficulties made it impossible to recover the transponder without 

 endangering the submersible. 



Subsequent tests of the system in similar situations has 

 shown that transponder navigation is probably not as reliable 

 in shallow waters as other navigational methods because of 

 error introduced when the length of the transponder base line 

 is the same as the water depth. In the case of our canyon study, 

 the base line was on the order of one to two thousand meters, and 

 the water depth was not greater than 1,500 meters. Also the 

 steepness of the canyon walls and the narrowness of the canyon 

 axes tend to introduce side echos which further increase the 

 unreliability of this method. 



