EarthScope-Oceans

MERMAID is a marine scientific instrument platform, short for Mobile Earthquake Recorder for Marine Areas by Independent Divers. MERMAID evolved from a first prototype, operational today, commercialized by OSEAN SAS in Le Pradet, France. Fourth-generation models add hydrographic monitoring capability to complement the acoustic sensor suite, and are... designed to carry out measurement profiles to depths exceeding 4,000 m. MERMAID is a freely-drifting float equipped with a hydrophone to collect hydroacoustic data for the study of earthquakes worldwide. Typically floating at a parking depth of 1500 m, the instrument uses a buoyancy engine (a hydraulic oil bladder system) to return to the surface for triggered data transmission (on average every 67 days) via the Iridium satellite constellation, to respond to on-demand data requests, and to receive mission parameter updates. MERMAID carries lithium-ion batteries, sufficient to power about 250 descend/ascend cycles, which translates to an instrument autonomy of about 5 years. A pressure sensor monitors descent depth, and a GPS receiver provides location and time corrections during the brief intervals that MERMAID surfaces (on average less than one hour). Fourth-generation models are multidisciplinary and carry a conductivity-temperature-depth sensor to collect hydrographic profiles of ocean temperature and salinity (similar to those from the Argo program) during their voyages. They can be additionally equipped with high-frequency hydrophones for the study of, e.g. cetacean (whale) vocalizations, and other sensors.Read More