The Placement of Sonobuoy and Sound Surveillance Systems in Strategic Straits to Support Underwater Defense Systems in the Archipelagic State of Indonesia

ALKI waters as strategic straits are Indonesian seawaters that have complex characteristics and are prone to infiltration by foreign ships. Currently, the Indonesian Navy is still focusing on security at sea level, while with current technological advances, many foreign submarines are using the underwater area to commit transnational crimes. The area under the water surface that is used is the shadow zone, which has the potential as a hiding place for submarines. The shadow zone is a safe zone where the temperature and salinity of the layer reflect the propagation of incoming sound waves so that submarines can avoid detection by Sonar. This paper aims to provide an alternative solution to the use of acoustic tomography technology by installing the Sonobuoy and Sound Surveillance System (SOSUS) to monitor the movement of foreign submarines entering Indonesian territory, especially through strategic straits. This study uses mixed methods, to process quantitative data from the questionnaires from the respondents regarding the criteria and alternatives to determine the coordinates of the Sonobuoy placement with the Analytic Network Process (ANP) and the detection probability theory approach. To process the quantitative data (shadow zone and submarine detection), the researchers simulated and modeled sound wave propagation from SOSUS using the parabolic equation method which was processed using MATLAB and the Act up v.2.2L toolbox, and processing qualitative data from interviews with experts would be analyzed to complete the quantitative data. The results of the research showed that the optimal placement priority and number of Sonobuoys were obtain. From the optimization of the sound wave propagation simulation by paying attention to hydro-oceanographic data in the form of temperature, salinity, and speed of sound. It is also obtaining the placement position and number of SOSUS with the concept of fixed sonar array operation, which is expect to be able to know the shadow zone and detect foreign submarines to support the underwater defense system in the Indonesian archipelago