UACE: Full Chain In-Situ Calibration of Hydroacoustic Hydrophone Stations

• Day: June 16, Monday
    Location / Time: A. TERPSIHORI at 11:00-11:20
• Last minutes changes: -
• Session: 04. Comprehensive Nuclear-Test-Ban Treaty Monitoring, and its Civil and Scientific Applications
  Organiser(s): Georgios Haralabus, Mario Zampolli, Tiago Oliveira, Mark Prior
  Chairperson(s): Georgios Haralabus, Tiago Oliveira
• Lecture: Full Chain In-Situ Calibration of Hydroacoustic Hydrophone Stations
  Paper ID: 2114
  Author(s): Ata Can Corakci, Mario Zampolli, Dirk Metz
  Presenter: Ata Can Corakci
  Abstract: Hydroacoustic hydrophone stations of the Comprehensive Nuclear-Test-Ban Treaty Organization’s (CTBTO) International Monitoring System (IMS) network continuously monitor the global oceans for nuclear-test explosions. The stations are equipped with hydrophone elements in triplet configurations placed in the SOFAR channel, where the speed of sound reaches its minimum, to detect acoustic events. Acoustic signals detected by the hydrophones are conveyed to the deep-water node section, which contains the electronics that convert the analog signals into digital signals, via analog riser cables. These signals are then transmitted to on-land electronics, housed at the Central Recording Facility (CRF), through fiber optic cables laid on the seabed. The full-chain calibration of a hydrophone station is currently performed once, in a laboratory setting before deployment. After installation at-sea, the calibration of the hydroacoustic station is performed from the CRF up to the node section without the contribution of the analog part that contains information related to the hydrophone and the riser cable.\nThe in-situ calibration of IMS hydroacoustic hydrophone stations, from the hydrophone to the on-land electronics, is important for assessing the state of health of the full chain and presents challenges. Key challenges include performing calibration in the low frequency spectrum range (1-100 Hz) and in deep-water conditions (maximum hydrophone depth of 1400 m). Since the hydrophone is the primary sensing component and a critical part of the hydroacoustic station, full-chain calibration with active underwater source has the potential to provide valuable additional information regarding the overall receiving sensitivity level of the station. The proposed approach can help to evaluate the status of the receiving voltage sensitivity of the full chain and support the assessment of station sustainability. The current approaches for low-frequency underwater acoustic field calibration will be presented, and the feasibility of on-field calibration techniques will be discussed.
• Corresponding author: Mr Ata Can Corakci
  Affiliation: CTBTO-IMS-ED
  Country: Austria