Signature – Day 8

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Usually the last to see us leave and first to see us arrive was a very rusted and derelict looking Russian AGI.  It would sit in international waters waiting for her catch – a U.S. submarine.  These ‘fishing trawlers’, as the Soviets called them, were actually spy ships who were attempting to keep track of, among other things, the departure and arrival of American submarines.  We almost always could expect a visit from one when leaving or arriving.

They also liked to show up when one of our boats was test launching a missile.  These AGIs, which was the moniker given to them by the U.S. military meaning “auxiliary general intelligence“, would usually track along side us but would also occasionally cross behind us in our wake or, sometimes, even attempt to cross in front of us – this was always the most risky and concerning maneuver that the AGI might pull.

The pictures below were taken one time when I was on the bridge and we were departing for sea.  If you look closely, you can see members of the AGI crew on their bridge – we would often wave back and forth to each other mostly just to get a rise out of each other.

agi2Of course, the intelligence analysts supporting the AGIs were attempting to understand the operational routines that we practiced when transiting in and out of ports.  Also, the AGIs were attempting to capture and subsequently develop a signature for each of our boats.  Like people and fingerprints, there are tell-tale characteristics that a boat has that can be used to identify any boat from another at a later time.  AGI’s would not only take pictures of our boats – all of our boats were black and didn’t have hull numbers and looked mostly the same to make it harder for visual identification – but they would also be listening for radio emanations, machinery  noises, and screw markers.

Interestingly, each and every transmitter, machine, and screw has its own unique sound characteristic.  Armed with these signature sounds all stored in a large database, then, an intelligence analyst can literally identify which boat is what later when contact is made with the boat.  Also, if detection is made later and most of the sounds are the same but one is slightly different, it might be assumed that some maintenance has since been performed or, more interesting to an analyst, something has been upgraded or modified.  This kind of data is all very interesting to the intelligence community.

It also goes without saying, perhaps, that if a boat is identified when leaving and then is detected weeks or months later somewhere far away from where it left, the analyst can calculate speed, bearings, routes, and so many other operational methods of the transiting boat.  Collecting sounds and noise and then being able to store it and later create signatures is, obviously, a potent tool to use against an adversary.

agi1To limit or preclude the collection of signature information, we would do various things when encountering an AGI.  To prevent collection of radio signatures, we simply would not transmit unless absolutely necessary.  It was common practice to maintain radio silence when leaving and pulling in.

And to cover machinery and screw noises – this was the fun part – we would do something very simple but also very creative and effective.  There were a number of times that I was on the bridge when departing or arriving and – to look at it – it seemed our boat was sitting in a bubbling whirlpool.  All around us, there were big bubbles gurgling and foaming up to the surface from under our boat.  Unfortunately, this method of preventing detection made us mostly sonar blind, but at least it also masked our boat noises from the AGI sitting off to our side.

What we would do is this – we would set what was called a low pressure blow out of all of our external ballast tanks.  Basically, what was happening is what happens when you blow into your drink straw.  Air is blown out and the result is big and noisy bubbles that rise up to the surface and pop gurgle pop.  This really can create a lot of underwater racket – so much so that machine and screw sounds are masked – and prevent anyone from picking up on our signature sounds.

We might transit like this for several hours – a big black mean looking submarine moving through the water with bubble foam all around it.  It was like we were one big noisy black floating Alka-Seltzer gurgle.  And the guys on the AGI wouldn’t get our sounds this time.  Sorry, comrades!

We almost always knew where the AGIs were patrolling – we received regular reports with their positions.   These poor guys were, of course, homeported somewhere in Russia and would have to sail the Atlantic to the U.S. eastern coastline and basically patrol up and back and up and back in an attempt to catch a U.S. boat.  Sometimes we would intentionally avoid them.  What was also interesting – or sad – is that the only port that they could visit for some R&R was Havana.  Oh my.

Understand, too, that the U.S. has these kinds of ships all over the world who also sit off of the coasts of various countries listening and watching.  Watching and listening.  It is all apart of the way business is done in the world of cat and mouse.

A memory…

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