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

40 多年来，声学跟踪的地下漂流者为了解深海流提供了独特且有价值的视角。最新一代的 RAFOS 浮标（SOFAR，或倒着拼写的 Sound Fixing And Ranging）——目前提供了观察窄流的可变路径、涡流的轨道运动以及表面以下污染物扩散的唯一手段。借助额外的传感器，RAFOS 浮标可以监测生物过程、测量垂直梯度并观察垂直速度，同时跟踪特定的水域。凭借其高分辨率跟踪（由一系列系泊声信标提供）和在大水平区域传播的固有趋势，声学跟踪浮标与广泛使用的系泊海流计和 Argo 浮标相得益彰。可以说，如果没有声学跟踪浮标，人们对地下海洋中连贯结构的丰富性及其对热量、盐、营养物质和其他水特性传输的影响的认识就会大大降低。尽管从声学跟踪浮标中获得了许多见解，但它的未来仍不确定。一些核心电子设备多年来一直没有现代化。成本和复杂的压载要求限制了更广泛的使用和新增强功能的开发。通过这笔资助，主要研究人员将开发下一代 RAFOS 浮标，使其更小、成本更低、更高效、能力更强且更易于使用。新设计的核心将是最近完成并经过测试的“Fish Chip”，这是一种微芯片上的声学接收器，旨在使用停泊声信标来跟踪鱼类。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。作为这笔拨款的一部分，主要研究人员计划将 Fish Chip 与完整 RAFOS 浮动功能所需的其他组件结合在一起，包括任务调度和通过铱进行的数据传输。新型“Fish Chip (FC) RAFOS”将内置新传感器、主动浮力控制单元以及小型声学高度计以增加水底跟随能力。五个原型机将在墨西哥湾进行短期现场演示并进行测试。预计 FC RAFOS 浮标将吸引新用户，并由于增加了新传感器端口、更低的成本、更简单的压载和水底跟踪功能，将开辟海洋学研究的新领域。凭借其小尺寸和最低功耗要求，微芯片上的完整 FC RAFOS 接收器可以添加到任何自动驾驶车辆中，以进行远程声学跟踪。

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.