SOSUS network operation & processing issues - Bay of Bengal

Above the seabed SOSUS array detects the submarine's sounds and the array automatically informs the shore station (on the left) or nodes of the array can pass on acoustic, VLF or ELF signals to alert the ASW corvette(?) above. (Artwork of  SOSUS array from Intelligence on Russian SOSUS 2016).

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Following SubMatt's March 13, 2019 article. A SOSUS or Sound Surveillance System can be an array of seabed mounted listening devices (hydrophones) linked by a high bandwidth optical fibre cable to shore(s). Also raw signals can go by tethered buoys, beamed up to satellite, then on to shore or ships at sea.

A SOSUS cable may be strung from Port Blair to Indian Eastern Naval HQ, Visakhapatnam (above) or to Chennai, all on the rim of the Bay of Bengal. The SOSUS cable might detect and triangulate an SSK diesel engine even if the submarine is (say) 1,000 km away in the Indian Ocean. As the submarine gets closer to the SOSUS array many additional submarine sounds can be discerned, eg. SSN reactor water/steam circulation, generator-gearing-electrical motor sounds from SSNs and SSKs, dropped tools and water “swishing” over the hull sounds.

Cavitation sounds might be picked up from Chinese SSNs over 15 knot (?) submerged cruising speed and SSKs over 5 knots (?) submerged cruising. Within 100 km (?) the diesel sounds of an SSK might reveal an individual SSK – even identifying an SSK known to be captained by a particular commander (maybe judged by his manoeuvring habits). Identification of submarine type or actual submarine is much easier if there are already recordings of the submarine’s sound on an Indian supercomputer database (aka electronic “dictionary” or “library”).

The Bay of Bengal SOSUS is likely to be connected to shore stations at Visakhapatnam. These may house supercomputers monitored by Indian Navy and maybe NTRO analysts who particularly want to determine what type of submarine are making noise, as well as its course and speed. Submarine types of particular interest include Chinese Songs, Yuans or Bangladeshi Ming SSKs and Chinese Type 093 SSNs.

Once the sounds have been processed-identified they need to be sent to the right naval assets eg. Naval HQs Visakhapatnam and Mumbai and (via satellite or powerful shore radio station) to Indian ships, submarines at sea and Indian (confusingly called P-8I "Neptune"). Indian ships submarines can cued onto and then tail the Chinese, Pakistani or Bangladeshi submarines detected.

Pete