Designing a test buoy for improving the Deep-Ocean Assessment and Reporting of Tsunamis (DART®) system

Mooring performance improvement is one of the National Data Buoy Center's (NDBC) highest priorities for their Deep-Ocean Assessment and Reporting of Tsunamis (DART
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) program. A mooring failure results in the station becoming nonoperational due to the break in acoustic communications between the moored buoy and the Bottom Pressure Recorder (BPR). Mooring failures are very costly due to the additional ship time required to recover the adrift buoy and the replacement cost of the mooring. The buoys may also drift far enough away where recovery is no longer economically viable and the buoy is lost. The purpose of the DART
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test buoy is to operationally test medium frequency transducers and validate and tune the DART
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mooring models. The DART
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system currently uses low frequency transducers for acoustic communications as shown in Figure 1. The acoustic cone of the low frequency transducers requires a taut mooring to sustain continuous communications. Medium frequency transducers have a larger acoustic cone and therefore may use a slack mooring with resulting lower stress. The test buoy will be outfitted with several sensors that will provide data on ocean currents, tension in the upper mooring and motions of the buoy and upper mooring. Other additional benefits of the test buoy are to operationally test primary lithium battery packs and to access an Acoustic Doppler Current Profiler (ADCP) as a tool to determine DART
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station siting suitability.