Undersea spying and Flight MH370

May 02, 2014

Sophisticated underwater listening systems abound in the seas. It's hard to believe none picked up sound signals from the crash of the Malaysia Airlines plane.


By Joseph Chong For The Straits Times

THE Malaysian government's handling of the loss of Malaysia Airlines Flight MH370 in March has been criticised by many. Much of the criticism, however, is probably unfair.

The event is not only unprecedented, but the Malaysian authorities and the media may well have been recipients of deliberate misinformation from the various authorities involved in the search.

Underwater search capabilities are a very highly guarded area of military expertise. To accentuate the problem, the Indian Ocean is strategic to military planners in the United States, Australia, India, China and Japan. The extent and frequency of (naval) Exercise Malabar involving the US and India are a clear indication of this.

There are good reasons for believing that the black box of the missing aircraft will eventually be found.The British Indian Ocean island of Diego Garcia is not only a base for US strategic bombers and nuclear submarines, but it is also home to a hydro-acoustic data acquisition facility. A 150-tonne aircraft crashing into the Indian Ocean at high speed would have registered prominently on hydrophones around the Indian Ocean.

This is probably the reason that the search team is confident of the approximate location of the crash site despite finding no crash debris on the surface thus far. Satellite Doppler calculations appear to be a nice supplementary cover story.
The original US underwater listening system that was developed at the start of the Cold War was called Sosus - an acronym for Sound Surveillance System. Sosus was a chain of underwater listening posts located around the world with the primary intent of tracking Soviet submarines.

Sosus exploited a natural occurrence in the seas - the deep sound channel (DSC) or the sound fixing and ranging (Sofar) channel. This is a horizontal layer of water in the ocean at which depth the speed of sound is at its minimum. Sound propagates in the channel by refraction in a similar manner to the long-distance transmission of light in an optical fibre.

The Sofar channel thus acts as a waveguide for sound. Low-frequency sound waves within the channel may travel thousands of kilometres before dissipating. The existence of the Sofar channel was discovered during World War II. Apparently, fin whales have been using the channel to communicate with one another over long distances.

Sosus consisted of seabed-mounted hydrophones connected by underwater cables to facilities on land. The hydrophone arrays were installed mainly on continental shelf slopes and other locations optimised for undistorted long-range acoustic eavesdropping.

The combination of location within the ocean and the sensitivity of the hydrophones allowed Sosus to detect sound transmissions of less than a watt at ranges of several hundred kilometres. The system was sensitive enough to hear Soviet submarine periscopes being raised hundreds of kilometres away.

Sosus proved itself "in battle" during the Cuban Missile Crisis of 1962 when it tracked Soviet nuclear ballistic submarines travelling submerged to Cuba. These were intercepted and forced away. In 1968, the Soviet Union lost the K-129, a ballistic missile submarine, north of Hawaii at a depth of 4.9km (comparable to the estimated depth of MH370). Despite a massive search, the Soviets could not find K-129 and gave up.

The US, using Sosus, was able to ascertain K-129's location to within a mere 5 nautical miles (9.26km). A US nuclear submarine, USS Halibut, using powerful sonars, eventually found the wreck.Using the cover story of deep-sea manganese exploration, the US carried out a clandestine operation to salvage the K-129 in 1974, without the Soviets finding out. It must have been a major intelligence coup because the details of the operation are still classified, even after 40 years.

Sosus has also helped to ascertain the splashdown point of Polaris ballistic missiles. Likewise, MH370's water impact would have probably generated shock waves that would have been detected by the hydrophones of the successor system to Sosus.

When the Cold War ended in 1991, Sosus was revamped to make it cheaper and more efficient to run. It morphed into the Integrated Undersea Surveillance System (IUSS). IUSS is the successor, the son, of Sosus. The personnel operating IUSS are an elite group of highly trained experts within the US Navy.

The US does not have a monopoly on Sosus-like systems. Britain has had an extensive system installed in the North Atlantic since the start of the Cold War. Japan is said to have one around its coasts. The South Koreans have also been installing one with US assistance.

It is very likely that the Australians and Indians also have one around their coastlines.

The physics of a submerged submarine is similar to that of an aircraft flying through water, and a quiet submarine is like a stealth bomber. The better non-nuclear submarines can launch torpedoes, anti-ship missiles and cruise missiles that can hit targets with little warning, far inland. A good example is the latest German-built Dolphin-class submarine of the Israeli Navy.

Part antidote to these dangerous submarines is a Sosus-like system and keeping the capabilities of such a system a secret as far as possible.

MH370 is a tragedy for all who have lost loved ones. But the true history of the search for it will probably only be known to the intelligence agencies involved.


The writer is a former investment manager now taking a break to write a book. A trained naval architect, he was a defence engineer in the 1990s.