Collaborative Research: The Next Generation RAFOS Float: A More Capable, Cost-Effective Subsurface Drifter for Observing Deep Ocean Currents

40多年来，声学跟踪的海底漂浮物为研究深海洋流提供了独特而有价值的视角。最新一代的浮标被称为RAFOS浮标(Sofar，或向后拼写的Sound Fixed and Range)--目前提供了唯一的手段来观察窄流的可变路径、涡流的轨道运动和表面下的污染物扩散。有了额外的传感器，RAFOS浮标可以监测生物过程，测量垂直梯度，并在跟随特定水域时观察垂直速度。声学跟踪浮标具有高分辨率跟踪(由系泊声信标阵提供)和覆盖大片水平区域的固有倾向，是对广泛使用的系泊海流计和Argo浮标的补充。可以说，如果没有声学跟踪的浮标，人们对次表层海洋中连贯结构的丰富性及其对热、盐、营养物质和其他水性质传输的影响的认识就会少得多。尽管从声学跟踪的花车中获得了许多见解，但它的未来是不确定的。一些核心电子产品已经多年没有现代化了。成本和复杂的压载要求限制了新改进技术的更广泛使用和开发。有了这笔赠款，主要研究人员将开发出更小、更低成本、更高效、更有能力和更容易使用的下一代RAFOS浮标。新设计的核心将是最近完成和测试的“鱼芯片”，这是一种微芯片上的声学接收器，已经开发出来，可以使用停泊的声信标来跟踪鱼类。它包括一个完整的接收器(前置放大器、相关器、到达时间算法和数据存储管理)，以及一个用于测量温度和压力的10位数字化仪。作为这笔赠款的一部分，主要研究人员计划将鱼片与RAFOS浮动系统全部功能所需的其他组件结合在一起，包括任务调度和通过Iridium的数据传输。内置在新的‘鱼片(FC)RAFOS’将容纳新的传感器，一个主动浮力控制单元，并提供一个小型声学高度计，以增加底部跟踪能力。五个原型将在墨西哥湾进行短期现场演示和测试。预计FC RAFOS浮标将吸引新用户，并开辟海洋学研究的新领域，因为它增加了用于新传感器的端口，成本更低，压载和海底跟踪能力更简单。由于其体积小，功耗要求低，在微芯片上完成的FC RAFOS接收器可以添加到任何自动驾驶车辆上进行远程声跟踪。

For over 40 years, acoustically tracked subsurface drifters have provided a unique and valuable perspective on deep ocean currents. The most recent generation?called the RAFOS float (SOFAR, or Sound Fixing And Ranging spelled backwards)-- presently provides the only means by which to observe the variable pathways of narrow currents, the orbiting motion of eddies, and dispersion of pollutants below the surface. With additional sensors, RAFOS floats can monitor biological processes, measure vertical gradients and observe vertical velocity while following a specific patch of water. With their high-resolution tracking (provided by an array of moored sound beacons) and inherent tendency to spread over large horizontal areas, acoustically tracked floats complement the widely used moored current meter and Argo float. Arguably, without acoustically tracked floats, there would be much less awareness of the richness of coherent structures in the subsurface ocean and their impact on the transport of heat, salt, nutrients and other water properties. In spite of the many insights gained from the acoustically tracked float, its future is uncertain. Some of the core electronics have not been modernized for many years. Cost and sophisticated ballasting requirements limit more widespread use and development of new enhancements.With this grant, the principal investigators will develop the next generation RAFOS float to be smaller, lower-cost, more efficient, more capable and easier to use. The heart of the new design will be the recently completed and tested 'Fish Chip' an acoustic receiver on a micro-chip that has been developed to track fish using moored sound beacons. It includes a complete receiver (preamplifier, correlator, time-of-arrival algorithms, and data storage management), as well as a 10-bit digitizer to measure temperature and pressure. As part of this grant, the principal investigators plan to bring together the Fish Chip with the other components necessary for full RAFOS float functionality, including task scheduling and data transmission via iridium. Built in to the new 'Fish Chip (FC) RAFOS' will be accommodations for new sensors, an active buoyancy control unit, and provisions for a small acoustic altimeter to add bottom-following capability. Five prototypes will be constructed and tested in a short-term field demonstration in the Gulf of Mexico.It is anticipated that the FC RAFOS float will attract new users and open up new areas of research in oceanography as a result of the addition of ports for new sensors, lower cost, simpler ballasting and bottom-following capability. With its small size and minimal power requirement, the completed FC RAFOS receiver on a micro-chip could be added to any autonomous vehicle for long-range acoustic tracking.