MACS brochure
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Mobile Acoustic Characterization System -- MACS The Exocetus Development LLC Mobile Acoustic Characterization System [MACS] was developed under company IR&D funding. The Exocetus [x-o-seatus] Coastal Glider [CG] is the platform for carrying all of the MACS sensors. Like the CG, the MACS is designed to operate in coastal waters where high currents and large water densities occur due mostly to the fresh water entering these coastal waters from rivers. The MACS can be programmed to operate in a 2 km square pattern around the oil platform at a speed of about 0.5 m/s and operating at depths from 10 m to 200 m depth. One complete circle of the platform would take about 4-5 hrs. However, initially, the glider would surface every hour so that an estimate of the current conditions can be made. The MACS can then be programed to operate at various speeds for each leg of the loop around the platform. After adjusting for current conditions, the MACS then report after one complete loop of the platform. Additionally, a second initialization of the glider operations would determine the radiated noise characteristic of the platform in both a horizontal and a very limited vertical directionality. This background noise characteristic of the platform would then be used to estimate the SPLs that mammals would be exposed to as they pass the platform. These sound pressure levels [SPLs] would be estimated based on the propagation losses calculated with the sound velocity profile determined by the CDT during operations around the platform. There are some major concerns about the amount of underwater energy that is propagated from offshore oil platforms, and the support vehicles attending these platforms, regarding their effects on marine mammals. The MACS incorporates some new underwater technologies that will allow investigators, in a very costeffective manner, to more easily characterize the noise fields around these offshore platforms. These new technologies include the Exocetus CG that can operate in areas surrounding the offshore platform for more than 60 days. Additionally, the sensor suite includes smart hydrophones that provide both event detection capabilities, as well as directional estimates to various platform noise sources. Other background noise levels would be established for the operation of supply vehicles of ships or helicopters. If the platform was a semi-submersible unit, the radiated noise estimates would also be based on the operations of the thrusters used to maintain position. Operational Capabilities The MACS has a speed capability of +1 m/s and an adaptive ballast control system to automatically operate in waters with density variations form 7 ppt to 37 ppt. Both of these conditions are frequently seen in the GOM around near shore oil platforms. The glider has sufficient size and power capacity to install three Ocean Sonics smart hydrophones [HF and LF versions], a Meggitt [Maryland] vector sensor unit, and a SeaBird GPCTD sensor. The primary lithium battery pack on the MACS has a capacity of 14 kW-hrs, and an extended version of the battery pack is rated at 21 kW-hrs. An acoustic modem can also be installed to operate with a surface gateway buoy or unmanned surface vehicle. The Ocean Sonics hydrophones are programmed to detect various types of mammals expected in the area of the platform – with three hydrophones, fifteen a priori events can be programmed. These events could be tonals or broadband signals depending on the FFT processing used on each hydrophone. Additionally, data stored on the MACS would be used for post processing the data after the 60-day operational period is completed. Once a mammal is detected with the event detector, a bearing estimate can be made with the Meggitt [Maryland] Vector sensor. 1444 East 9th Ave., Anchorage, AK 99501 USA Tel: 907-227-8073 | sales@exocetus.com | www.exocetus.com

If the acoustic data determines that a mammal is in very close proximity of the platform, the MACS would be programmed to come to the surface and report the findings to the platform via cellular phone or spread spectrum telemetry system. Another operational mode would be to telemetry the findings to a USV operating nearby so that the Exocetus MACS would not have to come to the surface. Meggitt [Maryland] VS-301 Vector Sensor On CG Narwhal The following types of MACS are now in our fleet of gliders: • • MACS – Basic: Three Ocean Sonics Smart Hydrophones [LF and HF]. MACS – Directional: Three...