High-resolution Autonomous Underwater Vehicle (AUV) Backscatter Grids - Caswell Sub-basin, Browse Basin Marine Survey (GA0345/GA0346/TAN1411)

Geoscience Australia (GA) conducted a marine survey (GA0345/GA0346/TAN1411) of the north-eastern Browse Basin (Caswell Sub-basin) between 9 October and 9 November 2014 to acquire seabed and shallow geological information to support an assessment of the CO2 storage potential of the basin. The survey, undertaken as part of the Department of Industry and Science's National CO2 Infrastructure Plan (NCIP), aimed to identify and characterise indicators of natural hydrocarbon or fluid seepage that may indicate compromised seal integrity in the region. 
The survey was conducted in three legs aboard the New Zealand research vessel RV Tangaroa, and included scientists and technical staff from GA, the NZ National Institute of Water and Atmospheric Research Ltd. (NIWA) and Fugro Survey Pty Ltd. Shipboard data (survey ID GA0345) collected included multibeam sonar bathymetry and backscatter over 12 areas (A1, A2, A3, A4, A6b, A7, A8, B1, C1, C2b, F1, M1) totalling 455 km2 in water depths ranging from 90 - 430 m, and 611 km of sub-bottom profile lines. Seabed samples were collected from 48 stations and included 99 Smith-McIntyre grabs and 41 piston cores. An Autonomous Underwater Vehicle (AUV) (survey ID GA0346) collected higher-resolution multibeam sonar bathymetry and backscatter data, totalling 7.7 km2, along with 71 line km of side scan sonar, underwater camera and sub-bottom profile data. Twenty two Remotely Operated Vehicle (ROV) missions collected 31 hours of underwater video, 657 still images, eight grabs and one core.
Following shipboard multibeam mapping, higher-resolution multibeam data were acquired in targeted areas (prior to instrument failure) using a Kongsberg Simrad EM2000 system mounted to Fugro's Echo Surveyor V (ES-5) AUV. This instrument had a depth rating of 3000 m, and surveyed the seafloor according to a pre-programmed mission plan. The AUV was fitted with a camera and light system designed to produce images of equal width and height (in the context of this survey, the images comprised 8 m by 8 m of seafloor). The equipment consisted of a light sensitive NEO 11 Megapixel 35 mm monochrome CCD (4008 x 2672) camera and two LED panels, each comprising 360 LEDs. High-resolution multibeam bathymetric data was collected together with side scan sonar and sub bottom profile data at an elevation of 30 m above the seafloor, and at line spacing's of 100 m. Overlapping high-resolution still photographs (captured every second) were then acquired on the survey lines at an elevation of 8 m above the seafloor. The AUV was equipped with an advanced real-time Aided Inertial Navigation System, which calculated the position, velocity and altitude of the vehicle and a HiPAP 500 USBL system was used to acoustically position the AUV.
This catalogue entry refers to the five  backscatter patches (A3 Patch 1, A3 Patch 2, A4 Patch 1, A4 Patch 2,  A4 Patch 3)  mapped using a Kongsberg Simrad EM2000 system mounted to Fugro's Echo Surveyor V (ES-5) AUV.

Tags: Australian EEZ, Exclusive Economic Zone, Marine Geoscience, Published_External, backscatter, geological storage of CO2, marine environmental baselines, marine survey
Organization: Geoscience Australia Data