@Machinbird,
Your deduction is on the ball. My only consideration would be if acoustic ducting was taking place, which may have been the case as I believe that the TPL was only at 250~300m depth when the #1 Ping detection was made, and the vessel was moving very slowly over the detection period.
There is some Doppler shift associated with the ping repetition period, and I believe that it is greater than the horizontal component of the vessel's speed. The residual looks as if it is due to the frequency decay on account of the continuing lowering of the battery voltage.
In summary, the current search may not turn up anything due to water depth increasing quite rapidly to the north, and possibly beyond a modified max pressure/depth that the Bluefin-21 can confidently do.
Last edited by mm43; 22nd May 2014 at 09:59.
Reason: added a letter to the first word