# Functionality of the Search and Rescue Transponder (SART) in Maritime Search and Rescue Actions
## 1 Introduction  
Modern maritime search and rescue operations involve several stages. The most significant of these are the analysis of large amounts of navigational, hydrometeorological, and traffic monitoring data, the calculations associated with a search or rescue plan, and the execution of the operation. Sophisticated systems and equipment, as well as modern technology, are used to support the operations. SAR (search and rescue) services mainly conduct these operations, but non-rescue vessels, including cargo, passenger, specialized, fishing, and recreational types, may also participate. Searching at sea carries significant risks. The probability of locating survivors depends on the accuracy of data on the coordinates of the accident, time of the accident, weather conditions, correct calculation of the reference position, knowledge of the type of object searched for, and many other data. The use of detection aids by survivors gives them a better chance. However, these devices must be operated correctly. Rescue vessels must also use their equipment properly to detect survivors. As statistics show, more than 80% of maritime accidents are related to the human element. Errors made by ship crews are often caused by the use of inappropriate procedures or insufficient competence. Training and increasing seafarers' knowledge are therefore essential in improving safety at sea. One of the most effective devices for search and rescue operations at sea is the SART radar transponder--Search and Rescue Transponder. The SART is a portable X-band(9 GHz, 3 cm wavelength) device that operates at standard marine radar frequencies. It is used to transmit a distress signal passively. When it is turned on, it waits to be activated by surface or airborne units' radar waves, and it reflects the signal. Marine SARTs are available as basic radar SARTs or the more advanced GNSS-supported AIS-SARTs (which also operate within the Automatic Identification System--AIS). A SART can be operated directly from the deck of a sinking ship or from a survival craft, such as a lifeboat or liferaft. For the best detectability, it is recommended that the minimum height above sea level be 1 m. When activated by radar waves, it creates a series of dots (echoes) on the radar display. The closest of these echoes is the approximate position of the transponder. The radar image changes depending on the distance from the radar (Figure 1). To receive the SART signal, a properly adjusted radar is required. The most important radar settings include range, operating mode, display mode, pulse length, and clutter filter. The SART is not a device that ships use on a daily basis; it is an emergency tool specifically designed for emergency situations. As such, detailed knowledge of its operation may be limited. A visual check of the device is carried out by the navigation officer once a month. However, the device is usually tested only once a year. More frequent testing is not recommended due to the risk of battery drainage. The test involves turning the device on and observing the response signal on the ship's radar. The distance between the device and the radar antenna is generally not large during such a test, as it is constrained by the size of the vessel. While the device can be placed at the edge of the vessel (e.g., stern or bow), in most cases, the distance will not exceed 100 to 200 m. At such short ranges, the navigator will typically observe full circles. It is not possible to test the device under different conditions. When abandoning a ship in an emergency, seafarers must be familiar with the procedures, take the SART device with them to the survival craft, and ensure the device is properly fitted. For the device to be detected, vessels passing nearby must have their radars properly tuned. Any errors made by the radar operator or the survivor may reduce the effectiveness of the device. Such a situation occurred recently.