A commercial safety device serves as a submarine sensor
By RICHARD R. BURGESS, Managing Editor
An electronic identification system designed for commercial shipping safety is now giving U.S. Navy submarines an additional passive surveillance capability. The Automatic Identification System (AIS) improves ship collision avoidance during navigation of ports and narrow waterways, and provides submarines a means to passively and positively identify and track a ship in its vicinity.
The shipboard AIS performs as an identification transponder, a device similar to those in aircraft that allow air traffic-control systems around the world to identify and track individual planes. The AIS can update its data as often as every two seconds for near-real-time accuracy. With a shipboard radar display overlaid onto an electronic chart display, an operator can plot the locations of all AIS-equipped ships within radio range, showing a ship’s name, heading, course, speed, latitude, longitude, classification, radio call sign, registration number and the contact’s discrete International Maritime Organization number, a code matching to a particular ship.
In February, Adm. Mike Mullen, chief of naval operations, ordered the installation of a standalone AIS capability onboard all submarines in order to enhance real-time situational awareness and overall maritime domain awareness. The order was issued after a team formed by the commander of the Pacific Fleet’s submarine force developed a plan to field the capability until a formal program could be established.
The attack submarine USS Annapolis, deployed in the Mediterranean Sea when the installation order was received, was one of the first six submarines to have AIS installed. It was retrofitted with the system in one day during a port call at Souda Bay, Crete.
The system uses an already-resident receiving antenna mounted on the submarine’s No. 2 periscope mast, allowing it to passively receive AIS transmissions from other ships while the periscope is protruding above the water. Unlike AIS installations on commercial ships, the submarine’s AIS normally does not give away the submarine’s position. For occasions when the submarine captain would desire to actively transmit his submarine’s position, such as entering or leaving port, a portable antenna can be installed on the bridge.
“For most purposes, you do not need to actively radiate,” said Cmdr. Don Neubert, commanding officer of the Annapolis during its recent deployment, noting that guidance from the submarine force governs when active AIS transmissions are allowed for subs.
Neubert praised the situational awareness capabilities of the AIS, collision avoidance being the most obvious. AIS gave his crew more situational awareness when coupled with systems such as the submarine’s sonar, radar, visual and electronic surveillance systems, providing another input to its contact management system.
During a transit of the densely trafficked Straits of Gibraltar, AIS gave Neubert an overhead view of where the merchant ships were, including their rate of turn, enabling him “to correlate those contacts with my onboard sensors, to make sure that I had the complete picture.
“Much like those other [sensors], you could use AIS, if required, for surveillance,” he said.
With only a periscope exposed, submarines can passively receive AIS signals, allowing for instant identification of a contact of interest, without the crew laboriously flipping through profile diagrams of ships to identify the ship.
The cost of an AIS installed has dropped from more than $9,000 to only half that amount as installation and procurement procedures have been refined, according to Katie Eberling, spokeswoman for the Intermediate Maintenance Facility, Pacific Northwest, at Naval Base Kitsap, Wash., the facility that conducted the first installations of the system.
“We were initially surprised at the utility and value of the system,” said Lt. Andrew Ring, navigator of the ballistic-missile submarine USS Nevada, which used AIS extensively on its most recent patrol. “Relying on radar and visual observations to generate a target solution can take time; now AIS can inform us almost instantaneously of all the contact’s parameters.”
A commercial safety device serves as a sub sensor
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Posted 18 August 2006 - 12:53 AM
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