SART – Search and Rescue Transponder

In emergency situations at sea, the Search and Rescue Transponder (SART) plays a critical role in the survival of many. SART helps accurately locate the position of a ship or life-saving appliance by detecting and responding to radar signals. Let’s explore this vital life-saving device in detail below!

What is SART?

SART (Search and Rescue Transponder) is a device used in maritime emergencies to determine the location of a vessel if it becomes lost or disabled.

There are two types of SART: Radar-SART and AIS-SART, which are based on GPS positioning. SART devices are brightly colored, handheld, battery-operated, and made from waterproof components.

SARTs are used on ships, lifeboats, and life rafts, and are designed to remain buoyant for an extended period even if the vessel sinks.

According to GMDSS regulations, ships with a gross tonnage (GRT) between 300 and 500 must be equipped with at least one SART, and ships over 500 GRT must have two SARTs onboard. They should be installed in easily accessible locations so that they can be quickly transferred to life-saving appliances. Most ships place SARTs on the bridge or near the bridge exit, and they can also be stored within life-saving appliances.

The bright orange color of SARTs makes them easy to spot, while the combination of a transmitter and receiver allows them to send and receive radio signals.

SARTs have played a crucial role in rescuing many vessels and ships by responding to search signals sent from X-band radar, typically at the 9 GHz frequency range. These signals are known as position-fixing signals.

The response is usually displayed on the radar screen as a series of dots on the X-band radar, guiding rescue teams to the distressed vessel.

Operating principle of SART

The Search and Rescue Transponder (SART) is a crucial device for ensuring maritime safety, featuring several outstanding characteristics. Constructed from fiber-reinforced plastic, the SART is designed to withstand prolonged exposure to sunlight and harsh weather conditions, ensuring durable performance in challenging maritime environments.

This device is brightly colored in orange to enhance visibility and is designed to float free from the life-saving appliance, ensuring it is always ready for use in emergency situations.

SARTs can be either portable or fixed to a life-saving appliance. Onboard a vessel, they are typically mounted on a fixed bracket attached to the ship’s bulkhead on the bridge. The device operates in the 9 GHz frequency band (9.2 to 9.5 GHz) and is specifically designed to work with X-band radar (3 cm wavelength).

The SART is activated by radar signals within the 9 GHz band from various sources.

When interrogated by radar, the SART generates a series of signal blips, creating a distinctive pattern on the radar screen. The SART is manually activated and only responds when queried by radar. In emergency situations, it emits signals that produce 12 dots on the radar screen, forming concentric circles as the distance decreases. These dots are spaced 0.6 nautical miles apart on the Plan Position Indicator (PPI).

The SART signal is more easily detectable than traditional radar reflectors, significantly improving search and rescue operations.

Additionally, the SART provides clear audible or visual indicators of its proper operation, alerting survivors when the device is being interrogated by radar. An audible “beep” is emitted every 12 seconds when no radar is in range and every 2 seconds when it is being queried by radar.

The combination of these features makes the SART an indispensable part of maritime safety equipment, designed to ensure the rapid and effective location of survivors in emergency situations.

AIS – SART

AIS-SART is an independent radio device designed to locate life-saving appliances or distressed vessels by transmitting updated position reports via the Automatic Identification System (AIS) Class A.

The position and time data for the AIS-SART are synchronized from an integrated GNSS receiver (e.g., GPS). The Global Maritime Distress and Safety System (GMDSS) mandates that one or more search and rescue locating devices be available. These devices can either be AIS-SART (AIS Search and Rescue Transmitter) or radar-SART (Search and Rescue Transponder).

AIS-SARTs are typically cylindrical in shape and brightly colored. A standard AIS-SART is about 10 inches tall and weighs nearly one pound.

Radar – SART

Radar-SARTs are used to locate life-saving appliances or distressed vessels by generating a series of dots on the radar screen of the rescue vessel.

Radar-SARTs are activated by X-band radar within a range of 15 km or 8 nautical miles. Each radar pulse received triggers a response from the SART, sweeping across the entire radar frequency band.

When interrogated, the SART quickly scans and then slows down to return to the starting frequency. This process occurs over 12 cycles, and at some point, the frequency of the radar-SART will match that of the interrogating radar, displaying a response on the radar screen.

This response appears as a series of 12 dots, spaced 0.64 nautical miles apart. These dots will appear larger as the interrogating radar gets closer, gradually turning into arcs until the SART is within about one nautical mile. The arcs will then become complete circles, indicating that the SART is active in that area.

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Reference information: https://www.marineinsight.com/marine-safety/what-is-search-and-rescue-transponder-sart/