Ascension Island hydroacoustic data system

The United States Air Force Technical Applications Center (AFTAC) is tasked with monitoring compliance of nuclear test ban treaties for the US. AFTAC utilizes several different techniques, each designed to monitor a specific physical domain (i.e. underground, space, oceans, etc.). Together, these monitoring systems, equipment, and methods form the US Atomic Energy Detection System (USAEDS). An essential part of the USAEDS is the Hydroacoustic Data Acquisition System (HDAS). The HDAS consists of underwater sensor systems linked to shore facilities with undersea data transmission cables, and shore based computers for data storage and transmission to the National Data Center (NDC). HDAS sensors are installed at Diego Garcia (Indian Ocean), Cape Leeuwen, Australia and Juan Fernandez Island, (South Pacific Ocean). Another HDAS system is to be installed at Ascension Island, a volcanic island located in the South Atlantic Ocean, with one array located north and one array south of the island, with cabling back to shore at Southwest Bay. In preparation for installation of the HDAS cable and sensors at Ascension Island, a detailed desktop study, marine cable route and sensor site survey and shore landing preparations were needed. The extremely remote location of the island and the volcanic nature of the island required unique approaches for the survey and shore landing operations. This paper describes the background of the HDAS installation and previous surveys at Ascension Island and provides an overview of completed and planned operations.