1The lesson in plain words
In one sentence…
A radar SART helps make survivors findable through suitable X-band radar and its matching sensor.
What does a radar SART show?
It responds to suitable X-band radar and creates a pattern from the approximate survivor position; nearby it can appear as arcs or concentric circles.
What identifies an AIS-SART?
It broadcasts locating information on AIS frequencies and uses the identity prefix 970; it needs an AIS receiver for detection.
How do you help detection?
Raise the antenna as instructed, keep it clear and remember that radar and AIS need compatible receivers.
What do you take to the craft?
Follow the muster plan and transfer assigned equipment, including the portable survival VHF, when safe.
2Step by step
SART and VHF survival workflow
- 1
Follow the muster plan and take the EPIRB, SART and portable VHF when safe.
Assigned equipment should reach the survival craft when possible.
- 2
Activate the locating device using its marked procedure.
Activation lets the equipment help locate survivors.
- 3
Raise the antenna at least 1 m above sea level, as instructed.
Antenna height affects equipment detection.
- 4
Keep the equipment exposed and monitor rescue instructions on the portable VHF.
Exposure and monitoring support detection and coordination.
- 5
Tell rescuers which device is active and what radar or AIS presentation to expect.
Rescuers must match the transmitter to the correct sensor.
- 6
Preserve batteries and follow approved test or replacement procedures after the event.
Post-event maintenance must follow approved procedures.
3Key data
- Radar SART standby
- 96 h
- Continuous interrogation
- 8 h
- AIS-SART operation
- 96 h
- Antenna height
- At least 1 m above sea level
- Radar SART response
- Twelve marks from approximate position
- AIS-SART identity
- Prefix 970
- Survival VHF
- Channel 16 and one more
- Batteries and testing
- Approved procedures
4Key points
- 1.
Radar SART and AIS-SART locate; the EPIRB complements alerting.
- 2.
Match the transmitter to its receiver before interpreting the display.
- 3.
Exposed equipment and a clear antenna support detection.
- 4.
The portable VHF supports coordination during rescue.
5Frequent mistakes
Wrong: "A radar SART always appears as an AIS target."
Right: Radar SART needs compatible radar; AIS-SART needs an AIS receiver.
Wrong: "The twelve marks are twelve survivors."
Right: They are repeated responses from an approximate position, not a person count.
Wrong: "I can hide the antenna and stop listening after activation."
Right: Keep the equipment exposed and monitor rescue instructions on VHF.
6Practice case & exam keys
Situation
A radar watch sees twelve marks spreading from a small craft’s bearing, while the AIS display shows no new target.
Which explanation fits the evidence?
Show the answer →
The pattern may be a radar SART; AIS absence does not disprove it.
Why: A radar SART responds to suitable X-band radar and produces twelve responses that may become arcs or circles nearby. An AIS-SART is a separate transmitter that requires an AIS receiving picture. The watchkeeper should verify radar compatibility, report the bearing and range, and use the survival VHF or other rescue communications to coordinate.
Exam keys
When you see «X-band radar» with «twelve marks», think radar SART, not AIS-SART.
When you see «prefix 970», identify AIS-SART and look for AIS reception.
If an option mixes radar SART with an AIS target, reject it: each device depends on its sensor.
How to read it
Picture three roles: EPIRB alerts, SART locates and portable VHF supports coordination.
A display is not enough: identify what transmits, what receives and how the signal should appear.
7Full lesson & sources
Open the full lesson (diagrams and official references)
A radar SART responds to suitable X-band radar and creates twelve marks extending away from its approximate position; arcs or circles can appear at close range. AIS-SART broadcasts locating information on AIS frequencies, with identity prefix 970. They locate survivors and complement the EPIRB alerting function.
Radar SART endurance is 96 h standby followed by 8 h continuous interrogation; AIS-SART requires 96 h operation. Raise the antenna to at least 1 m above sea level as instructed. Radar settings and equipment compatibility affect detection. Transfer the devices assigned by the muster plan to survival craft when safe. A survival-craft portable VHF provides channel 16 and at least one additional channel; use approved emergency batteries and testing procedures.
Two locating devices, two detection pictures
A radar SART responds when interrogated by a suitable X-band radar. On the radar display it produces a pattern of twelve marks extending from the approximate survivor position; at close range the pattern can appear as arcs or concentric circles. An AIS-SART instead broadcasts locating information on AIS frequencies and uses the identity prefix 970. Both devices help locate survivors and complement an EPIRB alert; neither replaces the other automatically.
Put the signal in the rescue team’s picture
Radar detection depends on a compatible radar, range, sea state, antenna height and line of sight. AIS-SART detection depends on an AIS receiver and the device’s transmission and antenna conditions. Raise the equipment as directed, keep it clear of obstructions and transfer assigned equipment to the survival craft when safe. A survival-craft portable VHF supports channel 16 and at least one additional channel under the applicable equipment standard.
| Device | What the rescuer sees |
|---|---|
| Radar SART | Twelve X-band radar responses, changing form at close range. |
| AIS-SART | AIS target data with identity prefix 970. |
| EPIRB | A satellite alert and locating information where supported. |
A practical survival workflow
- 1Follow the muster plan and take the assigned beacon, SART and portable VHF when safe.
- 2Activate the locating device using its marked procedure and confirm the antenna position.
- 3Keep the device exposed and monitor rescue instructions on the portable VHF.
- 4Tell rescuers which device is active and describe the expected radar or AIS presentation.
- 5Preserve batteries and follow approved test or replacement procedures after the event.
Worked insight: twelve marks are not twelve survivors
The radar SART pattern represents repeated radar responses from one approximate position. It is not a count of persons, boats or range rings. At close range the display geometry changes, so the watchkeeper must interpret the pattern with radar scale, bearing and visual information. An AIS-SART’s identity prefix helps recognition in an AIS display, but it still depends on a functioning AIS receiving picture and does not guarantee rescue contact.
The IMO performance standards for radar SART and AIS-SART should be paired with the actual device manual. Battery endurance, antenna height and exact indications are equipment-specific; check the approved values in the manual for the fitted device.
This separation makes the drill coherent: alert the rescue system, make the craft findable, then listen and respond.
Official references · 2026-09-09
8Test your knowledge
What can a pattern of radar responses from a craft represent?
Keep studying…
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