EK80 Water Column Sonar Data Collected During DAFT4-C11-201801 Deployment

A bottom moored echosounder was deployed at 47.15 m depth in the NE Chukchi Sea (70.0130N, 166.856233W) from 12 August 2018 to 26 August 2019. The mooring was instrumented with a battery powered EK80 wideband autonomous transceiver (WBAT, Simrad AS). The echosounder operated an upwards facing depth-rated 70 kHz 18° split-beam transducer (ES70-18CD), positioned upward with a two-axis gimbal equipped with a 0.7 kg counterweight. The echosounder also operated a combined 38 kHz 18° split-beam and 200 kHz 18° single-beam (ES38-18/200-18C) mounted at a fixed position. Both transducer faces were positioned at a height of 0.8 m above the seafloor. During the deployment, the WBAT was programmed to transmit an ensemble of 300 narrowband (200 pings at 70 kHz, 100 pings at 38 and 200 kHz) and 50 wideband (25 pings at 70 kHz, 25 pings at 38 and 200 kHz) every two hours. Data were recorded to a range of 60 m. This instrument failed after recovery and was unable to be calibrated, thus the mean values from the calibration of five other deployments were averaged. In addition, the 38 kHz channel failed during deployment, identified by issues the transmit power and impedence on the 38 kHz channel 2 in the raw files. Calibrations had occured in Seattle, Washington either prior to deployment or after recovery using a 38.1-mm tungsten carbide sphere following the standard sphere method (Demer et al., 2015).