An acoustic signal propagation experiment beneath sea ice

A polar environment presents unique operational challenges for Autonomous Underwater Vehicles (AUVs). Each ice environment whether it be sea, fast or shelf poses risks with significant consequences for AUV missions. Deployments can be coordinated via vessels or on-ice camps. The science and operational specifications on missions preclude shepherding of the AUV and result in a reliance on longer range acoustic signal transfer for communications and localization due to the typically lateral nature of the mission.In November 2009, a 10 kHz acoustic beacon system was tested for ranging capability and suitability of use for an emergency AUV location and monitoring system in the Antarctic sea ice environment. The system was deployed from the RV Aurora Australis north of the Australian Camp Davis. This work includes discussion on test plan formulation, prediction using simulation and field performance results of the acoustic system. Actual noise data and acoustic signal detection measurements are presented and compared with the simulation. Conclusions were drawn on deployment configuration and the testing setup. Proposed modifications will be evaluated in future experimentation planned for late 2010.

► Acoustic ranging performed in Antarctica with 10 kHz source beneath sea ice.
► Ranging results will help determine AUV survey mission parameters.
► 2 km ranging achieved in harsh environment.
► Simulation predicts 3 km ranging possible in sea ice.