Talk:SOSUS

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Engine noise[edit]

I removed:

In particular the widespread introduction of nuclear powered submarines meant that the sound of engines was no longer there to be heard, and instead the mechanical sounds of the motors and propellers would have to be used. To separate these sounds from the background noise of the ocean and other shipping required extensive sound processing systems to be installed.

as diesel-electric subs are actually quieter than nuclear powered boats when submerged. The reduced noise signatures of later boats is due to a variety of technical developments, not a switch to nuclear propulsion. Dan100 15:56, Feb 21, 2005 (UTC)

Not sure that this is necessarily a valid point. Whereas a good diesel-electric sub is quieter than a nuclear sub when running on electric power, such a sub could not move any great distance under electric power and certainly could not transit the entire area covered by SOSUS. A good nuclear sub IS quieter than a diesel-electric sub running on diesel power, and that's an important point. TomTheHand 15:40, May 8, 2005 (UTC)

Picture caption conflicts with article text, maybe[edit]

The article says the purpose was to cover the GIUK gap. The caption on the undersea (probably copyright violation) map shows the first sensors on the US eastern seaboard. I.e., completely out of range of the sensors. What gives? Piano non troppo (talk) 03:43, 20 August 2009 (UTC)[reply]

Someone dumped the following on the page[edit]

See https://en.wikipedia.org/w/index.php?title=SOSUS&diff=595126014&oldid=593543902 By user 80.156.46.177.

Outside of US territories were a number of other USNAVFACs such as RAF Brawdy in West Wales not far from Newgale beach (later moved to RAF St. Mawgan in Cornwall), Icemaiden in Norway and Inn Keeper located in Gibraltar. Indeed the Med and Eastern side of the Atlantic had other stations for example in Iceland the US operated 5 arrays from their Airforce base known as the 5100 series arrays. In the UK the 7100 series arrays included 7116, 7115, 7114, 7113, 7112, 7111, 7123, 7122, 7121 and the Fixed Distributive System (FDS) test bed were all operated from Brawdy, with 7116 being North of the Norwegian gap facing into the Norwegian sea and frequently detecting Soviet vessels as the came around the North Cape at ranges in excess of 1,000 miles. The other arrays ran Southwards with 7123 being off the French coast. Many array's were positioned off sea mounts or the edge of the continental shelf to reduce ambiguity as signal data was received into the beam formers. This is because the hydrophones were omni directional and received sound from different directions including reflection from behind the hydrophone sensor.


The detection range was often considerable and ranges over 500 miles were both frequent and constant. The low frequency coverage from zero to 100hz meant that refraction by temperature layers was insignificant. The Soviet power supply also helped as it ran at 50 cycles (as with most merchant ships) but the West operated ships and submarines with a 60 cycle power supply. Therefore detection of 50hz and harmonics of 50 hz was easy to analyse. The low frequency coverage of the arrays allowed the maximum recorded detection range of nearly 4,000 miles to be made although at these range targets were often intermittent and usually older Soviet vessels.


USNAVFACS performance was monitored based on Stats. These stats were essentially detection times from the moment the target first showed frequency lines to the time taken to recognise and record that data. Friendly detection were included in this and these allowed crews to reduce their detection times considerably because friendly vessels issued subnotes with position course and speed details provided in advance. Therefore NAVFAC crews would position themselves around the beams where the vessel would first show, and make a quick detection call to reduce stats. It was common to have a single operator standing by the beams and a second stood by a console with half of the data already entered in the system, such that when the first lines showed, the second operator merely pressed the enter button and detection was recorded as just a few seconds. For Soviet vessels their sailing times, course and speeds were also shared through intellegence updates and were also generally accurate enough to do the same trick when recording stats.


Inside the NAVFACs were banks of paper recorders known as LOFAR grams. These recorders were called fountain displays as the stylus printed the first frequency line along the bottom of the page, and subsequent lines below it thus pushing the paper trace upwards in a fountain movement. Detecting a single or multiple set of frequencies lines as the paper came up over the roller was the objective so stats could be recorded quickly to keep detection times low. The lowest frequency would be towards the left hand side of the paper. The recorders were set in banks corresponding to the number of beams on any given array. For example 40 and 32 beam arrays were common, and this meant that a single array could have 40 paper recorders in a line from beam 1 to beam 40. Each beam had an approximate bearing angle, although sound would often show on multiple beams at the same time. Cross detection from 2 or more arrays was always preferred - although not often possible - as this would give a cross bearing and almost instantaneous range to the target. The operators would walk the beams studying frequency lines as they printed, and most arrays had two or more operators plus supervisors walking the beams to minimise missing targets.

The arrays and corresponding recorders would show prinicpally narrow band frequency tonals related to either mechanical noise from the vessel or flow resonance due to the vessel moving through the water. From a mechanical perspective it was possible to see blade rates, turbine rates, the number of poles on motors and other such detail. The flow rates and mechanical rates were used to identify a given hull of a specific class. However the arrays also detected biological noise such as Whales and other marine species, along with wideband/broadband noise. The arrays would also detect seismic activity as very low frequency lines. The arrays would also detect low flying aircraft such as MPA (Maritime Patrol Aircraft) and indeed the prop or turbine speed could be calculated from the frequency detected leading to classification of the aircraft.

A basic Soviet submarine signature could consist of, 50 cycle power supplies, with a 6 pole ships services turbo generator rein-enforcing the harmonics at 300 hz (6x50), supplemented by gearing lines and propulsion lines. Therefore a Soviet type 2/3 nuclear submarine with a planetary gearing system and a reduction ration of 17.02:1 at 8knots would show a shaft rate of 52 hz a blade rate (5 bladed) of 10.4 hz, a turbine rate of 177hz. The sun gear, planets and ring gear mesh rates would also show on occasions. Additionally pumps, flow induced resonance and other discrete tonal could be detected particularly at close range. Needless to say all vessels had their own signature and most hull numbers within a class were also known. The Soviet type 2 and 3 had the same propulsion system but were different vessels. The type 2 Charlie/Victor classes were SSGN and SSN and the type 3 Yankee and Delta classes with SSBNs. The type 2 was a single shaft and the type 3 two shafted vessels. Most were 5 bladed although some older vessels had 4 blades and some newer Victor III had 7 blades.

During the 1980's the Soviets sent 5 Victor III submarines across the Atlantic towards the US Eastern seaboard on an exercise. Of interest was hull 9 which had undergone some significant noise reducion measures during a recent refit.

All vessels were detected both from Iceland’s arrays and through Brawdy in Wales (UK) before being handed over the arrays State side. Hull 9 was very quiet but at speeds below 6 knots became invisible to the arrays apart from two principally FIRs (flow induced resonance) frequency lines. The significance of these lines was that one was port side and the other starboard side and became separately more pronounced with speeds below 6 knows and if the vessel turned. Therefore when showing we not only knew that the vessel was below 6 knots but if she turned we could tell if it was to starboard or port. Above 6 knows she became much louder and as she increased speed the FIRs disappeared to be replaced by other more noisy lines. I recently watched a TV programme where a Soviet military officer spoke of the exercise and stated that these vessesl crossed the Atlantic undetected. This wasn't true all vessels were tracked continually although hull 9 was difficult to track on accasions. Had the requirement to take out the vessels occurred then this would have happened quickly.

In a second incident a lone Soviet type 2 Victor III sailed from the Northern fleet base and travels to the med. For the entire 3 months she was tracked without loss and at specific times she was bounced by NATO MPAs who were guided to the vessel by IUSS. The vessel would be located by the MPA who would either drop a cammand activated sonar bouy on the vessels position or would fly low over the area and thus be heard by the vessel where she would know she had been detected.

I watched this vessel in the Norwegian sea as she left Murmansk and rounded North Cape. She was handed over by a US Nuclear submarine (USS Dallas) to a British towed array ship and NAVFAC Iceland) the British vessel held steady contact 120 miles South West of the submarine and guilded a Nimrod MPA from the RAF on to the target. The aircraft stayed on task for around 1 hour before breaking off, then returned every 4 hours. Each time the aircraft would drop an active sonar bouy on the submarine to let them know they had been detected. Each time the aircraft went off task the submarine would increase speed to 30 knots (sprint) and head South to clear the area. This continued for 3 months. I always felt sorry for the Captain and crew of the vessel assuming they had no idea how they were being detected.

Integrated Undersea Surveillance System[edit]

I removed a link in the opening to the article "Integrated Undersea Surveillance System", since that article redirected to this one. Perhaps a better solution would be to retain the link, and delete the redirect, so the link here will be red until that article is started?? SlowJog (talk) 21:29, 8 March 2014 (UTC)[reply]

External links modified[edit]

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External links modified (January 2018)[edit]

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Weird present tense in the Chronology section[edit]

Is there any reason for the bizarre use of present tense in the chronology section? It's used inconsistently, is jarring to read, and doesn't make much sense. If there's no objection I might edit all of it out if I have the time and/or inclination. Brightnsalty (talk) 21:06, 20 January 2021 (UTC)[reply]

What "bizarre" use bothers you? Chronologies often flow with an "at this time this happened" style. To a large degree the text here paraphrases and maintains the style of the references. I would warn you that a real problem has occurred with some "grammatical changes" that changed the substantial meaning because the grammarian did not research references and understand the subject. The changes leading to the 01:37, 30 November 2020‎ revision was a reword driven by such a change. Getting rid of inconsistent tense or jarring points is fine, changing meaning is not. One problem that I recognize is that the chronology is a compromise between the bullet style of the early declassified history (when the less said was better) and more extensive later discussions of those events. Palmeira (talk) 21:33, 20 January 2021 (UTC)[reply]
It should be written in past tense, period. A bulleted list making use of the present tense would probably be acceptable, but there should be no compromise on accepted style guidelines. WP Ludicer (talk) 21:47, 13 April 2021 (UTC)[reply]
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