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Finland - Underwater Surveillance

Finland's interest in maritime surveillance is the Gulf of Finland: mean draft less than 25 meters, labyrinthine archipelago. Underwater surveillance in the Gulf of Finland is based on underwater listening devices, hydrophones, which are installed as fixed fields on the seabed. Underwater monitoring in the Gulf of Finland is quite good thanks to fixed listening devices. There is also a regular patrol warship in the Gulf of Finland called AKT-1. The acronym stands for safeguarding territorial integrity [alueellisen koskemattomuuden turvaaminen]. The ACP 1, a warship on duty, shall always leave for immediate surveillance, but not more than four hours. However, the ability of a single vessel to perform underwater surveillance is very limited. Normally, the action is focused on the surface. Sound conditions in the Baltic Sea are sometimes challenging. The ping signal of the sonar can bounce back from layers of water of different temperatures, causing even the submarine to go unnoticed. Just outside Helsinki, there are no such difficulties.

The underwater sound world opened up to the Navy in the 1930s, beginning with submarine water listening systems. The most sophisticated devices of that time were floating boats Iku-Turso and Vesikko. The first ones to land test on coastal listening systems were carried out in the years 1935-36. The results of these experiments were presented by Lieutenant Kalervo Kianen at the Military College as the tools and measures being demanded by Russian diving forces for combating their activities. In modern terms, this could be called the Navy's first concept of underwater warfare.

Development of domestic underwater monitoring systems began in the late 1960s, when the Naval Staff laboratory developed the Coastal Listener RKL-67. It was a 5-channel water listening system with hydrophone signals that could be stored on a lightweight reel tape integrated into the system. Using the same analog technology, a light 2-channela waterproof hearing aid VKL-71 was a mobile underwater surveillance.

Monitoring systems development work the 1970s, worked for the General Staff's Department of Electrical Engineering Research at Kivenlahti in Espoo. New features included the system digital control and hydrophone grouping pairs, which allowed the direction of audio input (ambiguous) based on the transit time delay of the assay. With this new system, the commercial production of the technology was transferred to Elesco Oy. The system was named m/80 and became by the end of the 1980s the main equipment for underwater monitoring by the Defense Forces.

The next step in the development was the three Hydrophone unit (racks) commissioning. Hydrophone mutual determination of travel time delays by correlation techniques listed the unambiguous definition of the direction of the sound. As an optionally based on phase information of the channel spectrumwas able to connect the input to the various frequency components of the audio direction. These features gave rise to a narrow-band monitoring system KVJ.

However, it found itself in a competitive situation when Finnyards Electronics (later Patria) provided the Navy linear antenna based on acoustic beam forming (hydrophone cable) system. The company had already delivered Helsinki class missile boats following the same principle PTA (Passive Towed Array). The Navy chose beam forming technology, which created a new PFA (Passive Fixed Array) system. The PFA series systems were installed on the coast by the mid-2000s.

The beginning of the millennium began with the transfer of underwater definition of the control system. The requirement was that underwater surveillance should be able to dynamically-to relocate the coast to underwater passages according to the current threat situation. New systemwas developed in collaboration with the Navy and Patria, and received renamed SURA. The devices lightness and mobility of the equipment was achieved through battery operation, ultra-low power electronics and optical fiber replacing the copper submarine cables fiber links. The SURA system was demonstrated in the year 2006, and came to complement the coastal fixed water supervision in the late 2010s.

SURA, the Rapid Deployment Underwater Surveillance System, is a new generation of lightweight, acoustic surveillance system that can be used in a wide variety of applications, from port security to area surveillance. The system configuration includes a variable number of lightweight sensors, a disposable fiber optic data connection, and a presentation and processing system. The system operates in both passive and active mode. SURA also provides connection to other sensor systems and C2I systems via LAN / WAN or other data connection. The SURA system responds to the need for performance by providing nearly heavy-duty fixed control systems with performance and portability as good as voice buoyancy systems.

In June 1982, a submarine was discovered west of the Åland Islands. Warning bombs were dropped into the water, after which the submarine fled Finnish territory. In August 1991, the Finnish Navy made a definite sighting of the submarine off Porkkala. When the submarine crew discovered they had been noticed, the ship fled. In October of the same year, a submarine was found near Russarö off Hanko. It was apparently a Russian boat observing the exercise of the Finnish Navy. In the west of Hanko, a probable submarine sound was made in November 1995. In August 2001, the submarine was searched twice during the week off Emäsalo and Porvoo. In August 2006, when suspicious noises were heard at Isonsaari monitoring station.

The most recent case reported was April 28, 2015. The Finnish Navy detected a potential underwater object in Finnish waters. The site was located in Finnish waters off Helsinki. Surveys were carried out on surface vessels and, based on the observations, a warning was also given with three hand-held bombs.

According to the Maritime Surveillance Guideline, an attempt is made to force a submarine into the surface for identification with a hand-held bomb. A handheld bomb is a grenade the size of a half-milk jar, which is thrown over the beard into the water. The bomb is timed to detonate after a certain amount of time after being dropped. The charge of the bomb is so low that it does not damage the submarine. The purpose of the handheld bomb is to inform the target that it has been detected.