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AIS-SART - The future Search and Rescue Transmitter

Apr 24, 2009
From January 1st 2010, after several years of product development and standardization work through international organizations, the AIS-SART will be adopted into the GMDSS regulations as an alternative to the Radar-SART.

The unique and innovative feature of the AIS-SART is the combination of its physical size and technical capability. The housing of the AIS-SART is identical to Jotron´s Radar-SART, type Tron SART20 - with total height of 251 mm and weight of only 450g.

Technically, the AIS-SART is based on the following principals; the unit will be programmed from the manufacturer with a unique ID code and receives its position via an internal GPS antenna. This data is combined and transmitted using the international AIS channels (AIS A and AIS B) in the maritime VHF band. 


How does it work?
The transmitter sends out a specified pattern. Every minute, a sequence of 8 messages is transmitted; each message is transmitted in a 26 ms time slot. 4 messages are transmitted on channel A and 4 on channel B. All 8 messages are transmitted within a total time frame of 14 seconds. This time frame is defined to maximize the probability that one of the transmissions hits a wave top. It is only necessary to receive one of the 8 messages from time to time to accurately locate the AIS-SART.

How do you know that this is an AIS-SART distress signal?
Anybody who can receive and detect an AIS signal will also detect an AIS-SART. The transmission signal from an AIS-SART consists of an MMSI like ID code, where the first three digits will be "970". The ID code consists of a total of 9 digits and the AIS-SART uses the remaining 6 digits to indicate a manufacturer code (2 digits) in addition to the unit's unique serial number (4 digits).
In addition to the ID code that appears on the AIS and connected equipment, an AIS-SART will also be visualized on an electronic chart, connected to the AIS transponder onboard. An AIS-SART will be shown as a circle with a built-in cross.

AIS-SART test results
As part of the process to define an international standard for AIS-SART, 3 different tests have been conducted by IEC / IALA. Jotron´s AIS-SART has been used as a test object in all tests. 

The initial test was done during the summer of 2008 in Oban, Scotland. The purpose of this test was to search for the AIS-SART using a ship, and to determine the required output power of the unit. The results showed that it was possible to detect a precise location from the AIS-SART at distances up to 8 &mdash 10 Nm (Nautical Miles). Similar results were obtained using the radar-SART, with the main difference being that the AIS-SART simplifies the search considerably because the position is plotted directly on the vessels electronic map system, because the AIS is a fully digital system. In addition, only one transmission of 26 ms is required to accurately get the position on the map, while the radar-SART requires continuous updates.

The second test was performed in Oban in September 2008. This test was to determine the obtainable range from a SAR helicopter. This test was done with a helicopter from the Maritime and Coastguard Agency (MCA), UK. Again, the results were as expected and the signals were picked up at distances between 26 and 40 Nm at flights levels varying from 300 up to 2500 feet.

The last test was performed outside Key West, Florida in January 2009. This test was performed by the US Coast Guard (USCG), using a C-130 SAR (Search and Rescue) aircraft. The aircraft flew at different flight levels at 1000, 5000, 10000 and 20000 feet and recorded the maximum range that could be obtained. A search for a 406 EPIRB and a radar-SART was performed at the same time to verify and compare the results that could be obtained with the results from an AIS-SART. The AIS-SART´s were deployed at different heights above sea level to account for different operating scenarios from a man over board unit to a SART mounted on top of a larger life-boat. 

The ranges obtained ranged from 40 Nm up to 132 Nm from the AIS-SART mounted on a 1m pole.

These range tests, together with previous tests performed from both helicopters and ships, show that the AIS-SART has a much superior performance compared with other locating transmitters (121.5, radar-SART). It can be located at a far greater distance, with GPS precision, using standard equipment (AIS) that automatically positions the persons in distress on a map. There is no doubt that the AIS-SART will contribute to a more effective and less time consuming search and rescue operations in the future, with the result that more people in distress will be saved!

The interest in Jotron´s new AIS-SART has been overwhelming, both from the market and authorities all over the world. Jotron expects to have a type approved AIS-SART during the summer of 2009. Furthermore, the AIS-SART will be implemented in an appendix to the European Marine Equipment Directive (MED), probably in the summer of 2010. In the meantime, authorities can issue national certificates to allow installation of the AIS-SART as soon as there are type approved products available.

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