Radar: a SART and a racon

What you do on the bridge

1. X-band, six miles
2. Find the SART
3. Range of the SART
4. AIS-SART
5. Identify the racon
6. Report and log

The oral questions, and what a good answer covers

The key points are in our own words. In the course, these questions come once you have done the job.

1. How does a SART show on the radar, and how does it change as you close it?Often asked

   A good answer covers:

   • Only on the X-band, 3 centimetre radar; the S-band does not trigger it
   • A line of about twelve dots running outward along its bearing
   • The dot nearest own ship marks the SART, very close to its true position
   • As you close to about a mile the dots become arcs, and very close they become circles
   • Reduce sea clutter and adjust gain carefully so it is not suppressed, and use a range of 6 to 12 miles to see it

   Show me on the bridgeA SART about seven miles ahead. Find the line of dots and say where the craft is.

2. At what range would you expect to detect a SART, and what limits it?

   A good answer covers:

   • At least 5 nautical miles from a ship radar with its antenna 15 metres up and the SART at least a metre above the sea
   • Range depends on the height of both the SART and the scanner, so hold it as high as possible
   • Sea clutter, rain and heavy seas hiding the craft can all reduce detection
3. What is an AIS-SART and how will you see it?

   A good answer covers:

   • A survival craft locating device that sends AIS position reports from its own GNSS
   • Shows on AIS displays, the ECDIS and the radar overlay as a circle with a cross
   • Its MMSI starts with 970 and the text says SART active or SART test
   • It gives a position, not just a bearing, and does not depend on radar band

   Show me on the bridgeTurn on the AIS overlay and find the AIS-SART beside the radar SART.

4. What is a racon, and how do you identify one?

   A good answer covers:

   • A radar beacon on a mark that answers the radar pulse
   • Shows as a Morse letter painted outward from just beyond the mark
   • The letter is printed on the chart beside the mark, so it identifies the mark
   • Many answer on X-band only; check the chart and the list of radio signals
   • It can hide a small target behind it, and rain or sea clutter controls, or a mistuned set, can weaken or hide it

How the lesson runs

The tutor's narration from the lesson, step by step. On the bridge, each control lights up as it is named.

1. Brief

   Both radars are running. Somewhere to the north-west a liferaft has its SART on, and there's a racon on a buoy to the west.

   We'll find the SART, put the EBL and VRM on it so we can give a bearing and range, check the AIS, identify the racon against the chart, and log it all.

2. X-band, six miles

   A SART answers only the X-band radar, so make sure radar 1 is on the display and transmitting. Put it on the six mile range, which shows both the SART and the racon clearly.

3. Find the SART

   Look to the north-west for a short line of bright dots, evenly spaced, running straight out from us. That's the SART.

   Lay EBL 1 along the line of dots.

4. Range of the SART

   The craft is at the inner end of the line, at the dot nearest us. The others are just the transponder's sweep. Put VRM 1 on that first dot.

5. AIS-SART

   Many liferafts carry an AIS-SART as well. Switch on the AIS overlay and look for a circle with a cross at the same place. It gives a position from its own GPS.

6. Identify the racon

   Now to the west-south-west. Just beyond a buoy echo you'll see a Morse letter painted outward: dash dash, the letter M. The chart shows the Scotland whistle buoy with racon M, so that confirms which mark it is.

   Put EBL 2 on the buoy.

7. Report and log

   A SART means people in the water or a liferaft. You'd call the Master at once and tell the coastguard, with the bearing and range. Now enter it in the deck log: the time, SART, its bearing and range.

The rules and guidance behind it

• IMO MSC.510(105): performance standards for search and rescue radar transponders (from 1 January 2024)