Design and Performance of a Two-Stage Mooring for Near Surface Measurements

Historically, the scientific mooring community has had a pressing requirement for the capability of installing lightweight easily deployed deep sea surface moorings to collect, record and/or transmit near surface measurements. Past surface mooring designs have not adapted themselves to provide a stable, low noise platform to eliminate the contamination of data caused by mooring motion. These requirements have now been addressed and a unique two-stage mooring has been designed to help alleviate these problems. The mooring incorporates braided KEVLAR mechanical and electro-mechanical cable to obtain a lightweight, compliant system which utilizes syntactic foam line floats as the main floatation. A series of trim floats at the air/sea interface used in conjunction with a stable low drag surface buoy results in decreased dynamic loading in the mooring line, which increases total system lifetime due to smaller fatigue values. Also, a new, hard polyurethane jacket on the electro-mechanical cable helps to protect it from possible fishbite attack. A complete mechanical system (void of electronics) was designed and deployed in a water depth of 1500 meters for a period of 4 months in the TOTO. The objectives of the test were to determine the mechanical compatibility and minimum lifetime capability of the mooring that could be expected in the ocean open. Also, the knowledge gained through this test will be used to optimize future designs for presently needed applications.