The processing is initiated in the depth sounder-receiver where the 

 signal is shifted, by heterodyne methods, to a lower frequency range. 

 The audio output of the depth sounder- receiver in this lower frequency 

 range is then processed by a frequency-modulated tunable discriminator 

 into a direct- current voltage. This voltage from the discriminator can 

 then be recorded on an instrumentation recorder together with Inter 

 Range Instrumentation Group B time. This recording is, as is the Doppler 

 shifted signal, an analog of the kinematics of the penetrometer. 



This recording can then be processed to obtain the depth of penetra- 

 tion and the velocities and decelerations of the penetrometer as it 

 entered the soil. 



DATA ACQUIRED 



Data from the Expendable Doppler Penetrometer is expected to provide 

 information on soil strength and penetrability and the occurrence of 

 anomalous conditions. In addition, the penetrometer data can be used to 

 extrapolate data between widely spaced cores. 



From the velocity data, deceleration can be obtained by differentia- 

 ting the curve of velocity versus time. This deceleration can be translated 

 into a deceleration versus depth curve. Deceleration at a point is 

 indicative of strength at a point. However, point data is not available 

 from the penetrometer because its length tends to average data. Neverthe- 

 less, changes in strength are apparent as the deceleration changes; hence, 

 the type of strength profile can be determined. Examples would be 

 uniform strength with depth, uniformly increasing strength with depth, 

 or soils with layers of different strength. An estimate of the magnitude 

 of strength with depth would also be available. The ' 'averaging' ' of 

 the penetrometer will mask changes if the layers are thin (say 3 feet 

 thick or less) or if the strength changes from layer to layer are not 

 significant. 



Penetrability is a general term to indicate relatively how easy or 

 difficult a seafloor would be to penetrate for a given penetrator. For 

 example, rock would be considered impenetrable for blunt, slow-moving 

 objects, and would have very low penetrability for a specially designed 

 ballistic anchor projectile. Soft clays, on the other hand, would have 

 high penetrability for a ballistically embedded anchor projectile. The 

 penetrometer should be a good tool for estimating relative penetrability 

 because it penetrates the seafloor during a test. Correlation with 

 anchor penetration data will enhance penetrability estimates. 



Data from the penetrometer can also be used to extrapolate between 

 widely separated core data. Often, when site surveys are conducted cores 

 are separated by distances of tens of miles and sometimes by hundreds of 

 miles. The gap between cores can be filled in with penetrometer data. 

 By performance of penetrometer tests near the cores and at intervals 

 between the cores, the core data can be extrapolated based on similarities 

 and differences observed in the penetrometer data. Changes in the 



