What is Search and Rescue Transponder (SART)?

SART/ Search and Rescue Transponder

SART/ Search and Rescue Transponder is used during maritime emergencies to locate a ship’s position if it goes off-track.

There is a radar-SART and AIS-SART, which is GPS-based. SARTs are brightly coloured, can be held in one hand, are battery-operated and made of waterproof components.

They are used in ships, lifeboats, and liferafts and are designed to remain afloat for long, even if the vessel sinks.

Per GMDSS regulations, ships between 300 and 500 GRT must carry one SART, and ships over 500 GRT must have two onboard. They must be mounted where they can be swiftly placed in a survival craft. Most ships have SARTs on the bridge or close to bridge wing doors. They can also be stowed in survival craft.

The bright orange colour of Search and Rescue Transponders ( SART) enables quick detection, whereas the combination of transmitter and receiver allows it to transmit and receive radio signals.

SARTs have been instrumental in rescuing several crafts and ships by reacting to the search signal sent from an X-band radar, typically of 9 GHz. These signals are known as homing signals.

The response is usually displayed on radar screens as a sequence of dots on an X-band radar, which helps rescuers reach the vessel in distress.

Watch the video on SART.

As mentioned earlier, SART is an electronic device that automatically reacts to the emission or interrogation by ship radar. This enhances the visibility of the party needing assistance on the radar display (PPI). SART operates on the 9 GHz band and only transmits when switched on and when interrogated by a radar.

SART – General features, location and functioning

• SART is made of fibre-reinforced plastic, which can withstand and bear prolonged exposure to sunlight and extreme weather conditions.
• It is capable of floating free of the survival craft.
• It is orange.
• SART is mounted on a mounting bracket, which is fixed to a bulkhead on a ship on the bridge.
• It operates on the 9GHz frequency band (9.2 to 9.5 GHz) and generates a series of clips on the radar it is interrogated by (3 cm/X Band radar).
• They can either be portable or fixed permanently into the survival craft.
• The SART is activated manually and hence responds only when interrogated.
• When activated in a distress situation, the SART responds to radar interrogation by transmitting a signal that generates 12 blips on the radar, which turn into concentric circles as the range between the two reduces.
• On the PPI, the distance between the blips will be 0.6 miles.
• This signal is very easy to spot than a signal echo from, say, a radar reflector.
• The SART also has an audio or visual indication of its correct operation and informs survivors when interrogated by the radar.
• An audible beep is heard every 12 seconds when there are no radars in sight and every 2 seconds when interrogated by radar.

Carriage Requirement

• Passenger ship- at least 02
• Cargo ship 500 GT and above- at least 02
• Cargo ship 300 GT and above- at least 01
• One on each survival craft

Battery Requirement

• In standby condition, operational for 96 hours
• In working condition, operational for 08 hours
• The battery should be replaced every 2 to 5 years
• Operable in temperature between -20 deg to 55 deg

SART Test Procedure

Self Test (General)

• Switch SART to test mode
• Hold SART in view of the radar antenna
• Check that the visual indicator light operates
• Check that the audible beeper operates
• Observe the radar display and see if there are concentric circles on the PPI.
• Check the battery expiry date

Self Test (Typical)

• Remove SART from the bracket
• Insert the probe into the SART at 2-second intervals; the lamp flashes and the beeper sounds.
• Observe concentric circles on the X-band radar.

In case of a false activation, switch the SART off immediately. T ansmit a DSC safety alert on VHF Channel 70. T ansmit a safety broadcast by RT on VHF Channel 16 to all stations indicating your ID and position and that you wish to cancel your false alert, which was transmitted in error.

AIS-SART

The AIS-SART is a self-contained radio device that locates a survival craft or distressed vessel by sending updated position reports using a standard Automatic Identification System class-A position report.

The AIS-SART’s position and time synchronization are derived from a built-in GNSS receiver (e.g., GPS). Global Maritime Distress Safety System (GMDSS) installations include one or more search and rescue locating devices. These devices may be either an AIS-SART (AIS Search and Rescue Transmitter) or a radar-SART (Search and Rescue Transponder).

AIS SARTs are usually cylindrical and brightly coloured. An AIS SART model is around 10 inches high and weighs almost a pound.

Radar-SART

A radar-SART is employed to find a survival craft or a vessel in distress by creating a series of dots on the rescue vessel’s radar display.

The radar-SART is triggered by X-band radar within a 15 km or 8 nm range. Every radar pulse received generates a response by the SART, which is swept across the entire radar frequency band.

When interrogated, it sweeps rapidly and then slowly to the starting frequency. This process occurs for 12 cycles, and at some point during this process, the radar SART frequency matches that of the interrogating radar, displaying a response on the radar display.

This is a line of 12 dots spaced by 0.64 nm. These dots will appear larger the closer the interrogating radar is, gradually becoming arcs until the SART is within one nautical mile. The arcs will turn into complete circles, showing the active SART in the general area.

Conclusion

SARTs are helpful in rescue operations involving aeroplanes or ships stranded by air or sea accidents. They are designed to survive the toughest conditions and stay active in elevated positions, like on a pole, to cover a diverse range. An aeroplane’s SART transponder could range from 30 to 40 miles. This helps to scrutinize a huge range and area.