Critical in the ongoing battle to detect hostile submarines is a little-known network of ocean sensors that support the more visible deployment of frigates and maritime patrol aircraft. Here we examine the history and development of this network, a key to UK maritime power.
The Sound Surveillance System (SOSUS) codenamed Project Caesar, began in 1954 as a classified US programme to use an extensive network of hydrophones laid on the seabed to track Soviet submarines. The technology was successfully refined and gave NATO a great advantage over their underwater adversaries throughout the Cold War. The UK has been fortunate to have involvement and access to this project since the early days. SOSUS had been built under the cover of civilian oceanographic research and was not made public until 1991. The Soviets were largely unaware of its importance until its existence and scale were revealed to them in the intelligence passed on to them by the Walker spy ring in the 1970 and 80s. Soviet submarines were notoriously noisy and easy to detect but, partly on learning of the passive detection capabilities of SOSUS, they began to build quieter submarines. In general US and RN submarines were considerably more stealthy but Russia has now closed that gap, its newest submarines are comparable to NATO designs in terms of stealth.
SOSUS comprised fixed, passive linear hydrophone arrays for long-range detection of the noise radiated by submarines. In simple terms, the noises from the machinery and the cavitation effects of a submarine propellor can potentially be detected hundreds of miles away because seawater is a very good conductor of sound energy. Using hydrophones at dispersed locations it is possible to triangulate and locate the source of the noise to a precise point in the ocean. The arrays were laid at strategic points around the Atlantic and Pacific and relayed information to shore stations via undersea cables. The shore stations were linked by satellite and phone lines. At its Cold War peak, SOSUS employed around 4,000 personnel working at 20 shore stations. In 1974 a SOSUS station was constructed at RAF Brawdy in Wales and by 1980 over 300 personnel were stationed there, analysing acoustic data gathered from arrays laid around the British Isles.
Dam Neck
In October 1995, NAVFAC Bawdy was closed and its functions moved to the Joint Maritime Facility at RAF St. Mawgan in Cornwall. In 2009 St Mawgan was closed and the combined USN and British operation was moved to Navy Operational Processing Facility (NOPF) at Dam Neck in Virginia. Data collected from ocean sensors across the Atlantic is now processed at this single facility before the intelligence is passed onto the frontline. (There is a parallel facility that serves the Pacific region at NOPF Whidbey Island in Washington State). It must be assumed that the analysis and submarine tracking information gathered here is passed on to the UK Joint Headquarters at Northwood to the RN Commander Maritime Operations (COMOPS) where it is used to cue submarines and warships to their targets.
Going mobile
By the late 1980s, SOSUS had evolved to become just a part of what is now known as the Integrated Undersea Surveillance System (IUSS). Purpose-built towed array sonar ships were integrated into the system in the form of the Surveillance Towed Array Sensor System (SURTASS) ships. Designed to be quiet, stable in all weathers and able to track targets at long range from the optimum location, their data is transmitted back to IUSS land stations by satellite. Unlike the SOSUS seabed arrays, they also incorporate Low-Frequency Active (LFA 100-500hz band) transducers that transmit energy into the water. If reflected back off the target, the sound is detected by the long passive arrays trailing behind the ship.
The RN does not have the luxury of single-role dedicated towed array platforms but 8 of the 13 Type 23 frigates carry the renowned Type 2087 system. RN submarines also deploy towed arrays which must be attached to the submarine by a support vessel before leaving for a patrol. Following the “Asia pivot”, SURTASS vessels now operate almost exclusively around the Chinese coast and Western Pacific but the USN is in the process of fitting all its destroyers and cruisers with a new TB-37/U Multi-Function Towed Array (MFTA) sonar system.
During the Cold War, the Warsaw Pact had deployed its own towed array platforms, although it is likely they were not as effective as Western equivalents. During ‘Operation Barmaid‘ in August 1982, HMS Conqueror was fitted with special pincers and undetected, managed to cut and steal an array belonging to a Polish AGI to be taken to the US for analysis.
The behaviour of sound waves in water varies enormously depending on conditions such as depth, currents, salinity and temperature layers. These variables will affect if, when and where submarines may be detected. The Royal Navy’s hydrographic ocean survey ship HMS Scott does not just collect data for creating charts but contributes oceanographic information for both submarine operations and anti-submarine warfare. Understanding the composition of the water column assists the deterrent submarines in knowing where they may be safest from detection. For the submarine hunter, understanding the composition of the ocean helps them predict how their sonars will perform. As submarines have become quieter, ASW has had to move back to a greater reliance on active sonar. Active sonar gives a more precise fix on the location of the target but has the disadvantage of immediately alerting the submarine that it is being tracked.
China and Russia spur renewed US ASW developments
The US is now in the process of making the biggest upgrade to the IUSS since the Cold War. The key component is the Deep Reliable Acoustic Path Exploitation System (DRAPES). This system will be far less reliant on potentially vulnerable seabed cables and utilises acoustic modems that pass data through the water, allowing the creation of something like an undersea wireless network. Wireless underwater communications have been available for some time but only at relatively low bandwidth and short range. Recent breakthroughs make it possible to scale this up and transmit much greater volumes of data further. Acoustic sensor data can be transmitted long distances through a series of nodes which may include other hydrophone arrays, Unmanned Underwater Vehicles (UUVs), Unmanned Surface Vehicles (USVs) or a surface buoy. Data is then either sent via satellite back to Dam Neck for evaluation or to nearby surface ships and MPAs.
The USN is also experimenting with the ASW Continuous Trail Unmanned Vessel (ACTUV). This long-endurance craft can deploy sonar specifically designed to detect and trail very quiet conventional submarines and will be another node on the network that feeds data via satellite to IUSS. The USN has already proved this concept with its Seaweb system designed for use in shallow littoral water less than 300 meters deep. DRAPES will be on a vastly bigger scale, and able to span the deep ocean. Reliable Acoustic Path Vertical Line Arrays (RAPVLAs), bottom-mounted, high-grain sensor systems, will be laid at significant depths in the open ocean where background noise levels are low. This gives them a very large field of view to detect submarines passing overhead. These are a maritime equivalent of a satellite and are known as subullites. The Reliable Acoustic Path (RAP) refers to the dense and quieter waters in the deeper parts of the ocean where sound transmission is more detectable and predictable.
Although submarines are getting even quieter and there is more man-made background noise in the shallower parts of the oceans than ever, IUSS has the advantage of the enormous computer processing power available today. Huge volumes of sensor data can be quickly analysed by computers to filter the background noise and amplify even the very faint telltale sound of the submarine.
The location of an explosion that points to the loss of the missing Argentine submarine ARA San Juan was established using ocean hydrophone arrays. The official story is that the source of the location was data gathered from hydrophones belonging to the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). It is possible that this is a cover story for a more accurate fix provided by the more sophisticated and extensive IUSS network, although its coverage of the South Atlantic is less than that of the North.
Recent reports of increased Russian submarine activity in the waters around Scotland and the GIUK (Greenland-Iceland-UK) gap probably stem from initial detections by IUSS sensors. The media has suggested we “rely on Scottish fishermen reporting when they see a periscope” but of course, the initial detections probably come from seabed hydrophone arrays or towed arrays trailed by frigates and submarines. NATO Maritime Patrol aircraft flying from RAF Lossiemouth or Keflavik Air Base in Iceland are unlikely to find a submarine by chance and must also rely heavily on this data to cue them to the approximate area before they can localise submarine contacts with sonobuoys.
The RN’s submarine force appears to have recovered slightly from the material defects that limited its operations in the last 18 months or so and the service is now described as “busy”. We can assume SSNs are much in demand to trail Russian submarines in the North Atlantic. Observing the recent increase in US Navy Virginia and Los Angeles class SSNs visiting Faslane also confirms this. IUSS, surface units and MPAs all contribute but a submarine is by far the best platform to detect another submarine and then keep on its tail.
This underwater battle of wits and technology has varied in intensity since submarine warfare began in earnest in World War I. Britain has twice been close to the brink of starvation and defeat as its lifeblood of merchant shipping was almost cut off by submarines. Today we are arguably more vulnerable to this threat than ever. The giant modern container ships that deliver goods to the UK may have cargoes valued in millions of pounds and transport the equivalent of a 50-ship World War II convoy. We are also reliant on a steady stream of tankers delivering LNG from the Middle East to keep many of our power stations going. Even one or two well-handled submarines could easily disrupt this shipping and quickly cause chaos and economic paralysis to the UK. For the RN to conduct carrier strike and other offensive naval operations, a prerequisite will be having the upper hand in the undersea battle. IUSS is a critical and little-known part of this fight, every penny invested in equipment, training and development of anti-submarine measures is money well spent.
The end of the Cold War eliminated much of the justification for maintaining IUSS at its full capability, with the existence and capabilities of SOSUS and IUSS being declassified in 1991.
We are not on a war footing and I see no reason to cause disagreements with other countries by laying an extensive network of sensors, unless done exclusively in our own waters.
Yeah right… we will submit your candidacy for National Security Advisor.
What a load of horse hockey.
Iqbal, you must live in a very utopian world.
Out current ASW force is too small, too few ships and especially submarines to work too much ocean. These forces cannot be created at the drop of a hat and crews trained and given experience.
Meanwhile hostile nations continue to grow their forces and carry out hostile acts.
I presume you have written a strongly worded postcard to the Kremlin and Beijing to ask them to to adhere to your peace and loving policy?
Most of the Seas and Ocean are outside any countries 12 mile limit. So all countries are at liberty to lay sensors. I would be shocked if the east has not at least attempted to put sensors off the west cost of Scotland and in the Western Approaches.
exactly, spot on………just another good bit of knowledge shown from Iqbal (again)
You have to remember that Iqbal is fundimentally anti-British. He wants this country reduced to a third rate, or fourth rate power like Austria. He wants the Royal Navy cut down until nothing is left and it can’t threaten his beloved masters overseas.
Therefore anything that is talking about capabilities he will say we don’t need them (regardless the actual truth). If there is any chance to make the navy look bad he will jump on it (even if it means bitching about things like “carriers without fighters,” I can only imagine well aware of the fact that they exist in that state due to cost cutting measures he’d have been first to advocate).
He doesn’t want more forces to be created at a drop of a hat if we need them. He wants us to not have them ever so we can’t impede the march of his beloved Islamic State, nor of his paymaster Putin.
In the cold war there were regular armed incursions on outlying places!
Iqbal is spot on. We should look beyond Cold War paranoia and strengthen our surface ASW fleet with the resources we have.
There is no evidence China or Russia have the technology to deploy these sensors or the political will to do so near our country.
But underwear arrays, by the sound of this article, provide a much more useful capability than frigates in strategic terms at a fraction of the cost.
If China or Russia can’t use these sensors for whatever reason (I doubt it’s a moral dilemma for them) then we should thank our lucky stars rather than willingly putting ourselves at a disadvantage.
Naive beyond comprehension. The reason for defence is deterrence and countering exiting threats. You might have missed the past few years of Putin and China’s cyber/territorial empire building in Ukraine and waters around Japan..the Cold War never ended, just as islamic fascism has and will not. Defence is an ongoing necessity-as for we’re not on a war footing, tell that to those daily blown apart by islam across the globe and the sociopath Putin flexing his (going by the topless photos) flabby muscles. Wake up to 21st century planet Earth – it’s an ugly situation.
i deeply admire the submariners and we should seriously be on our guard against Russian aggression. excellent article, thanks
The UK is the “Naval Bastion” of NATO. Recent plane and naval incursions from Russia prove that the “old game” is back on…if we want it or not. UK should do well re-assessing it’s defense posture. BREXIT does not mean that the UK will be able to return to some kind of “splendid isolation”. These days are long gone and were unproductive anyway.Now, what does the UK need in terms of defense is of course a national policy but as an outsider I would say to put your money on a strong Navy first, the Airforce second and the Army as a third. The next problem that has to be solved is this tendency of protracted policy, not uncommon in other european nations like France who seem to change direction at every windchange. The two carriers will be the cornerstone, they are flexible assets and can tackle missions a frigate can’t do. These two carriers should be given all the means they need to do the job, in close collaboration with the US. ( F35 and surely an ASW and AEW version of the MV22 ), just like the famous SEA-KING with the british version outpacing the original one. Brits are good at that, making US equipment better! Next I would urge you britons to have a look at the Italian Navy who seems able to produce ships and means on an intelligent basis and actually taking over some british idea’s, like their new 25000t amphibious carrier who looks quite british and has huge potential.Two of these would strengthen the fleet enormously at reasonable cost. Disinvesting in nuclear boomers with are more a pride thing than really useable might free up funds to reactivate a true submarine force to counter russian and other countries capabilities but making these boats also able to strike inland would generate a true intervention force. And last, Brits can not do it alone, working with the dutch, danish and belgian fleets woud be a game changer if a close cooperation could be activated. Dutch, danish and belgians could deliver escorts and other assets were the Royal Navy would be weaker. Just an idea…
In one hand you acknowledge that ‘The old game is back on’ and the Russians are a threat, then state we should give up the CASD.
I thought it was only politicians who didn’t think things through properly?
Also, if you truly believe that the UK is NATO’s naval bastion, perhaps look at the assets we have and compare them to the US.
Iqbal….what are you doing on this site? This is aimed at people who care about the RN and our countries defence in general, get yourself a hobby!
Today, Christmas day, is the anniversary of the sinking of SS Agberi and U-87. People probably won’t be on the site today, but if you are, then please feel free to have a look and remember.
https://rcahmw.gov.uk/the-war-at-sea-christmas-1917/
In event of heightened tensions, the rapid conversion of commercial vessels such as offshore supply ships or large trawlers, to carry a containerised towed array sonar eg http://geospectrum.ca/towed-reelable-active-passive-sonar-traps/ or https://www.thalesgroup.com/en/worldwide/defence/captas-1-variable-depth-sonar would seem to be a sensible step.
That still wouldn’t solve the problem of trained operators. This kit isn’t kept stacked on a warehouse shelf either. I would imagine several months lead time at the very minimum.
In addition, preventing a conflict by projecting strength is one of the main roles of a nations armed forces.
You’re right, it isn’t kept on a warehouse shelf but the point is, it could be and at much lower cost than dozens of extra frigates. Agree too that training operatives would be a priority but in this computer generated alternate reality that lots of youngsters live in today, I’d have thought that’d be right up their street.
If it were right up their street then I think we could presume they would be in the AFCO right now and solving some of the retention issues.
Frigates are expensive, but sometimes you have to invest in your assets. Unfortunately this government and others would rather privatise equipment, infrastructure and jobs. I will leave you to ponder why.
bit more to it than playing on a computer. Years of study and training to understand oceanography, marine acoustics and their application to military operations to be effective. Computers are just tools, fantastically powerful ones, but just tools none the less and useless without skilled operators to use them. In the UK the branches have merged as well, so we expect hydrographers to be meteorologists as well, further lengthening the training pipeline.
I agree with STRN. We are more vulnerable than ever. There is no depth to anything. Fewer merchant vessels carrying ever larger loads are easier prey and the world’s just in time inventory means everything grinds to a halt in double quick time. Big problem no one wants to even think about.
Quite the reverse to the comments of this being where peacetime savings should be made. The SOSUS/SURTASS nets are significant force multipliers.
Simply put, if you have an ability to sanitise large sections of seaspace with a surveillance asset, you know you dont have to put patrol assets in there. Effectively you can deploy and direct smaller ASW forces in a more efficient and effective manner.
The analogy is the advantage that AWACS gives to a defending fighter team. If you know where and when to position your forces you can do more with less. RN has access to SOSUS data clearly, but, the ability to have mobile, focused, long range UW coverage independent of that is a simply a ‘good idea’.
I’ve been an advocate of an RN SURTASS capability, similar to that the Japanese have deployed with their Hibiki-class, for a couple of decades. Now is precisely the time to bring that in…before anyone antagonstic has their bluewater SSN fleet really back up to speed.
I’m very sceptical about the idea that there are ‘advances in UW comms’ as mentioned in the article though. UW ‘wireless’ is dependent on acoustic modem technology and the problems with that providing high datarates over any realistic distance are fundamental. The signal to noise ratio (SNR) has to overcome the background sea/ocean noise floor. That requires a good deal of power behind the signal, which requires a significant power source, and makes it less than discrete. I’ve not heard of any new laws of physics being discovered that fundamentally alters the situation here.
I served in Gtmo, Cuba for 3 years at AAWC which was followed by 3 years at COMOCEANSYSLANT. Best duty ever!