AIS-SART stands for AIS Search and Rescue Transmitter. It is a portable emergency locating device that electronically marks the position of survivors or a survival craft at sea. It determines its own location and broadcasts position reports with a device identity through the Automatic Identification System, or AIS. The crew of a suitably equipped vessel or aircraft within reception range can recognise the target on its display and approach the reported position. The AIS-SART supports this on-scene search; an initial distress alert to a rescue coordination centre requires its own alerting path.
How position and identity are transmitted
Two separate functions work together inside the device. Its internal receiver for global navigation satellite systems, or GNSS, uses their signals to determine a position. The AIS transmitter then broadcasts the result in the maritime VHF band. The satellites provide the basis for the location; the emergency locating transmitter sends its AIS messages to receivers within reach. It does not wait for radar interrogation or a radio call.
Transmission uses the two AIS channels at 161.975 and 162.025 MHz. In active operation the device sends a burst of eight messages roughly once a minute, alternating between the channels. Repetition increases the chance of a message getting through while the device moves in a seaway. AIS Message 1 carries the position report with a status identifying an active emergency locating device; a periodically inserted Message 14 carries a short status text. This is a data signal. An ordinary voice radio cannot turn it into a position on a chart.
An AIS-SART device identity starts with 970. Further digits identify the manufacturer and individual unit. This identity refers to the transmitter, not the person in the life raft or a friendly military unit. Personal AIS man-overboard devices with a 972 identity and AIS locating transmitters incorporated in EPIRBs with 974 belong to different device groups. Several devices using AIS can therefore have different activation, alerting and attachment arrangements.
What a reachable search crew sees
Location requires a suitable AIS receiver, a working connection to a display and usable reception. Suitable navigation displays show the AIS-SART as a distinctly marked target alongside other AIS targets. The crew does not need a special radar SART setting for this. A radar alone cannot provide this AIS position, nor can a voice radio without AIS data reception.
Older displays may show the transmitter as an unnamed vessel with a 970 identity instead of the special AIS-SART symbol. The identity and received data then help identify the apparent vessel as an emergency locating transmitter. This creates a practical limitation for survivors: a person still has to recognize the received signal correctly and use it for a search. A flashing light on the survivor's own device does not reveal the remote display or the crew's attention.
The VHF radio path depends partly on the height of both antennas and obstructions between them. A low transmitter close to the waves faces different conditions from a high shipboard antenna. A coastline, a vessel's structure or poor device placement may obstruct reception. An aircraft can only benefit from its greater antenna height if it actually has suitable receiving and display equipment.
Using the equipment actually available
First check the device label: AIS-SARTs and radar SARTs require different receiving equipment. Secure the device against loss and carry out its marked activation sequence. Depending on the design, this may involve releasing protected controls and moving a switch into active operation. When a design requires manual activation, removing it from its bracket or putting it in water does not replace that step. If additional automatic activation is provided, the triggering conditions for that device apply.
Active emergency operation and test mode have different meanings. A function test may send an AIS burst explicitly marked as a test and then end automatically. Mistaking that indication for continuing emergency operation leaves the survivor waiting for an inactive device to work. In emergency operation, check the designated operating indication. If the device has separate indications for operation, a position fix and transmission, interpret each by its own meaning: switched on, a valid position obtained and a radio message sent are three different states.
Place the transmitter upright in its intended mounting arrangement. If a suitable mounting pole is available, extend and secure it. The antenna should be above water; the intended AIS-SART mounting arrangement aims for at least one metre above sea level. Use the appropriate fitting in a survival craft if one is available. Without a craft, establish the upright position above water that can safely be achieved with the means at hand. A buoyant device may float in a different attitude from its intended operating position. Allowing it to drift loose therefore combines the risk of loss with poor antenna placement.
The GNSS antenna needs access to sufficient satellite signals. An open position with a view of the sky helps it determine a fix; the VHF antenna also needs a radio path with as little obstruction as possible to receivers within reach. Keeping the unit deep inside a bag, beneath a metal cover or flat on the floor may impair these functions. After securing it, check its placement and designated indications again, particularly if waves or movement have shifted the mounting.
Battery condition limits operation. The expiry marking, previous activation, test consumption and visible damage all matter when assessing the available device. A light may still flash with an exhausted battery after the energy needed for AIS transmissions has run out. Such a fault indication has a different meaning from an indication that no position fix is available. Repeated testing uses reserve power. Do not try to charge the designated primary battery; a damaged case or opened battery compartment may also compromise watertightness.
Missing position, old reports and a lost transmitter
An AIS-SART can continue transmitting when its position source or time synchronization fails. Position data and their status must therefore be considered separately from transmission alone. A newly received radio burst may arrive without a new valid location. If the fix is missing, improve antenna placement and the view of the sky where this can be done without losing the device or putting the survivor at risk of falling or going overboard. Check position and operating indications using the meanings for the particular design; restarting the device does not replace missing satellite signals.
Even a previously valid point belongs to the report from which it came. If survivors keep drifting and newer valid position data or their reception are missing, the distance between that old point and their actual location grows. The receiver therefore needs to consider the age of reports and the condition of the position source alongside the identity. The survivor can help provide better data by maintaining correct operation and antenna placement, but cannot control a remote display.
The reported location always belongs to the device. If its attachment breaks and the transmitter drifts away separately, search forces may approach a working AIS target while the people remain elsewhere. The attachment should therefore keep it with the group or their survival craft. It must continue to hold after movement and wave action. An unreachable transmitter does not justify another fall or an unsecured jump into the water.
Distress alerting and military recovery
A radar SART answers a suitable search radar with an artificial radar pattern. An AIS-SART instead broadcasts position data autonomously to AIS receivers. A 406 MHz EPIRB uses the Cospas-Sarsat satellite and ground-station path to deliver a distress alert to the responsible rescue coordination centre. These functions complement one another. If such a distress beacon or another suitable connection is actually available and usable, it can provide the initial alert; the AIS-SART may later help a search force approach.
During military isolation, the device's open broadcasts can lead to detection by an adversary. A compatible receiver within range can interpret the identity and position regardless of which side its operator belongs to. The AIS-SART does not select a friendly recipient or authenticate an approaching force. When enemy observation is possible, the person must weigh the prospect of detection by available search forces against revealing their location. An adversary within reach can use the same position data.
The electronic mark helps a suitable force locate survivors once it actually receives and interprets the data. The AIS-SART itself has no AIS receiver and provides the survivor with no reception acknowledgement. Its operating, fix or transmission indication reports a state of the local device. Recognition by a crew, its response, communication during the approach and safe physical pickup remain further steps. Until pickup, the people must maintain flotation, attachment security and protection against cold using the means available.