Autonomous hydroacoustic stations in support of CTBT‐monitoring technology and event screening

No more than six hydroacoustic receiver stations will be monitoring the three world oceans in the framework of the CTBT. Together with five T‐wave stations they will synergetically cooperate with the seismic network which alone can neither provide the required accuracy of localization on the southern hemisphere nor the capability of reliable event discrimination of the oceans. To maintain the function of the sparse hydroacoustic network in case of an irretrievable station breakdown, an autonomous auxiliary unit for temporary replacement of fixed cable connected stations has been developed by FWG. The battery‐supplied autonmous station, like the permanent stations, suspends the hydrophone at the depth of the SOFAR channel axis. The lightweight construction permits quick deployment and retrieval. The received acoustic signals are processed for prescreening at the station by algorithms with adjustable criteria to discriminate large explosions from natural events of similar energy turnover such as sea quakes and volcanic eruptions. The characteristics of the signals are transmitted by a surface buoy radio link via low orbit satellites to the data center, together with unprocessed, highly suspicious signals for expert analysis.