# Functionality of the Search and Rescue Transponder (SART) in Maritime Search and Rescue Actions
## 2 Materials and Methods  
A typical marine radar transmits a high-power pulse stream at a fixed frequency in the 9 GHz band (9.2-9.5 GHz). It collects the echoes received at the same frequency and displays them. The SART device operates by receiving a pulse from the search radar and sending back a series of pulses in response, which the radar then displays as normal echoes. While the SART is being interrogated by the search radar, it continuously scans the radar band for radar signals. When the range closes so that fast sweep responses are detected, the first dot of the SART response displayed will be no more than 150 m distant from the true location of the SART. When the range is such that only slow sweep responses are detected (range approximately greater than 1 nautical mile), the first dot of the SART response displayed may be as much as 0.64 nautical miles beyond the true position of the SART. The radar-SART may be triggered by any X-band radar within a range of approximately eight nautical miles (15 km). In stand-by mode, the SART unit will wait 96 h for activation. Once activated, the transmission time is a minimum of 8 h.  
The radar settings affect its detection functions. The radar must be properly prepared and tuned. The condition of the radar is also crucial for proper image display. The accuracy of the displayed image depends primarily on the condition of the oscillator (magnetron), power, frequency band, resolution, sensitivity, gain, noise reduction, pulse length, and range. To assess the radar's transmission and reception power, the performance test is used, among other methods. Its primary function is to receive reflected signals from obstacles (objects), allowing the navigator to make anti-collision decisions. Radar settings can be adjusted manually or automatically. In automatic mode, the radar adapts to changing weather conditions, using features such as gain or clutter filters (e.g., sea and rain clutter filters) to eliminate interference from sea waves or rain, thereby improving the radar image quality. However, if the radar image is cleared too much, small objects will also be removed. Figure 2 shows the appearance of the radar screen along with the control panel. The ability to detect an object also depends on its size. It is practically impossible to detect small objects, such as people in the water. Depending on the distance, a liferatt may be detectable. To enhance the signal, the user of the liferatt should use a radar reflector. The radar reflector works by reflecting radar waves back towards the source. Unlike the SART device, the radar reflector has no mechanism or electronics (Figure 3). Figure 3: Radar reflector (**left**) and SART (**right**) placed next to each other on the liferatt. Figure 2: SART image on the radar [ECDIS Simulator NaviTrainer 5 Wartsila, Helsinki, Finland]. During a certain accident in 2022 [8], the survivor used the SART, but the device was not detected by any of the four ships' radars in the vicinity. The survivor was floating on the water's surface and did not use the telescopic extension; instead, he held the device upside down with his hands. This could have affected the device's range. The person was eventually rescued after several hours. An inspection of the device was conducted, and it was found to be operational and in good condition. The vessel's X-band radar settings were also checked, and it was found that certain settings, such as Auto mode, significantly reduced the SART device's detectability. No dots or circles were displayed on the screen, so the user was not notified of the SART detection. To study the impact of radar settings, the authors conducted a large-scale experiment in real sea conditions using a physical SART device and marine radar. The main objective of the experiment was to observe changes in the radar image when receiving the SART device's response. The specific objectives were:  
1. To verify the detectability of the device under different conditions (varying distances, radar settings, and the presence of the radar reflector);
2.