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物提供了一个独特的和有价值的角度对深海洋流。最新一代？被称为RAFOS浮子（SOFAR，或声音固定和测距）-目前提供了唯一的手段，通过它可以观察狭窄的电流，漩涡的轨道运动，以及表面以下污染物的分散的可变路径。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，并在跟踪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（由一组系泊声信标提供）和在大的水平区域传播的固有趋势，是对广泛使用的系泊海流计和Argo浮标的补充。可以说，如果没有声学跟踪浮子，人们对地下海洋连贯结构的丰富性及其对热、盐、营养物和其他水特性的影响的认识就会少得多。尽管从声学跟踪浮子中获得了许多见解，但其未来仍不确定。一些核心电子设备已经多年没有现代化了。成本和复杂的压载要求限制了更广泛的使用和新改进的开发。有了这笔赠款，主要研究人员将开发下一代RAFOS浮子，使其更小，成本更低，效率更高，功能更强，更容易使用。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，已经开发用于使用停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），以及一个用于测量温度和压力的10位数字转换器。作为这项资助的一部分，主要研究人员计划将鱼芯片与RAFOS浮标功能所需的其他组件结合在一起，包括任务调度和通过铱传输数据。内置到新的'鱼芯片（FC）RAFOS'将是住宿的新传感器，一个积极的浮力控制单元，并提供了一个小型声学高度计，以增加底部以下的能力。预计FC RAFOS浮标将吸引新的用户，并开辟海洋学研究的新领域，因为增加了新传感器的端口，降低了成本，简化了压载和底部跟踪能力。凭借其小尺寸和最低功耗要求，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.