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

40多年来，声学跟踪的水下漂流者为研究深海洋流提供了独特而有价值的视角。最近的一代？这种浮标被称为RAFOS浮标（SOFAR，也就是声音固定和测距的缩写），目前它是唯一一种可以观察狭窄洋流的变化路径、漩涡的轨道运动和海面下污染物扩散的仪器。通过额外的传感器，RAFOS浮子可以监测生物过程，测量垂直梯度，并在特定水域观察垂直速度。声学跟踪浮标具有高分辨率跟踪（由系泊声信标阵列提供）和在大水平区域内传播的固有趋势，是广泛使用的系泊流计和Argo浮标的补充。可以说，如果没有声学跟踪浮标，人们对地下海洋中丰富的连贯结构及其对热量、盐、营养物质和其他水性质运输的影响的认识就会少得多。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新增强功能的更广泛使用和开发。有了这笔资金，主要研究人员将开发下一代RAFOS浮标，使其更小、成本更低、效率更高、功能更强、更易于使用。新设计的核心将是最近完成并经过测试的“鱼芯片”，这是一种安装在微芯片上的声音接收器，用于使用系泊的声音信标跟踪鱼类。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10位数字化仪来测量温度和压力。作为这项拨款的一部分，主要研究人员计划将Fish Chip与其他组件整合在一起，以实现完整的RAFOS浮动功能，包括任务调度和通过铱星进行数据传输。新型“Fish Chip (FC) RAFOS”将内置新的传感器、主动浮力控制单元和小型声学高度计，以增加底部跟踪能力。将建造5个原型，并在墨西哥湾进行短期现场示范试验。预计FC RAFOS浮子将吸引新的用户，并开辟海洋学研究的新领域，因为它增加了新的传感器端口，成本更低，压舱更简单，并具有底部跟踪能力。由于其体积小，功耗低，集成在微芯片上的完整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.