10% is considered excessive and indicative of either insulation degradation with age or 

 possibly the result of data points taken at a gradient.* 



(6) Of eight, 1830 m probe drops from FLIP in 1974, seven were successful, while 

 in 1975, of eighteen, 1830 m probe drops from the ORB, only three were successful. 



Comment: 



Because the length of the 1 830 m probe wire link is four times that of the 460 m 

 probe, a higher failure rate is normally expected. Typically, Sippican experiences a success 

 rate of around 80% for this probe. The excessively high failure rate due to apparent wire 

 leaks during the ORB drop infers a possible problem stemming from the launch platform, 

 e.g., a high platform, perhaps, allowing a combination of wind and/or sea action to rub 

 the wire link against the ship's hull or mooring lines of other devices. However, the good 

 success rate (over 90%) for the two 460 m systems seems to rule out such a problem source 

 (assuming launch conditions were similar for all three systems). 



One additional source of problem can be accumulation of salt buildup and debris 

 around the lip of the launcher bell-mouth. If a third launcher, separate from the more 

 successful 460 m drops, were used for the 1830 m attempt, the possible presence of such 

 encrustation around the bell mouth, coupled v/ith wind and/or water motion, could have 

 produced some of the early failures experienced. Sippican suggests weekly inspection 

 and soft-cloth cleaning of the launcher mouth to prevent such problems. 



Finally, the possibility does exist that a group of faulty probes were encountered. 

 Assuming that the possibilities cited were not the cause of failure and that the probes were 

 less than two years old, Sippican's policy of replacement includes the 1830 m probe as well 

 as the 460 m.** 



(7) "Runs" of XBT profiles that measure within specifications but with a bias in 

 one direction rather than a random distribution. 



Comment: 



Besides occurring because of a miscahbrated recorder, such "runs" can also 

 result from the following causes. 



The thermistors employed in the probes are manufactured by a batch lot process 

 yielding several thousand at a time. The process produces units that are very similar 

 within a batch for slope. The units are then individually ground to value at one temperature, 

 which is periodically reset to centerline value after some degree of in-tolerance drift. Either 

 or both of these variances can produce thermistor lots that are within specification but 

 exhibit bias on one side or the other. 



(8) Individual units of "many" simultaneous pair drops showed excessive 

 differences in temperature at depth. 



Comment: 



A total of 90 out of 96 paired drops were visually acceptable (93.8%). 

 Comparisons were made at fixed apparent depth increments of 200 m, 300 m, and 400 m 



*See author's note C. 

 *See author's note E. 



138 



