Sub-bottom profiler data of Chukchi sea in Arctic ocean The SBP120 Sub-bottom profiler installed on ARAON in 2008 is an optional extension to the highly acclaimed EM122 Multibeam echo sounder. The receive transducer array shared with the EM122 is wideband. By adding a separate low frequency transmit transducer and electronic cabinets and operator stations, the SBP 120 has a capability of the sub-bottom profiling. The system beam width is 12 degrees with 24 transducers. During the survey the SBP120 is synchronized by the Synchronize Unit which controls the triggering timing to reduce interference between acoustic equipment such as EM122 and ADCP. It has a much narrower beam width than a conventional sub bottom profiler with correspondingly lesser smearing. It thus provides deeper penetration into the bottom, and higher angular resolution. The frequency ranges from 2.5 to 7kHz. Its beam is electronically stabilized for roll and pitch. It can also be steered to take into account the bottom slope. The ping rate is synchronized to that of the EM122 if both are running simultaneously. The topics are: - to examine sedimentary structure below the coring sites - to investigate shallow sedimentary structure - to reveal sedimentary structures related to ice ages.