Phased Testing at Sea of the Son-O-Mermaid Prototype

Son-O-Mermaid是一种完全自主的、长寿命的海洋地球物理仪器，该仪器将在巴哈马群岛近海进行为期三个月的海上测试，那里的深水很容易进入，海洋条件普遍有利且具有良好的特征。Son-O-Mermaid是一个自由漂流的浮标，它(1)从波浪作用中获取能量，足以为(2)一个垂直的水听器阵列提供动力，水听器阵列悬挂在一条连接到波浪下方阻尼板的电缆上，(3)一个全海洋深度回声测深仪，(4)定位和定时精度的GPS，(5)一个近实时数据传输的铱星通信单元，以及(6)机载数字化和处理单元。没有类似的工具存在。它的前身“MERMAID”在基本方面与我们的“Son-O-Mermaid”不同。MERMAID完全缺乏(1)(3)和(2)的数组方面。Son-O-Mermaid的功能(4)-(6)始终处于“开启”状态：仪器是自供电的，作为一个整体，从未完全淹没在水下。Son-O-Mermaid将由未经训练的人员从机遇船上部署，这使得它比传统的方法（例如海底、系绳、系泊）具有额外的优势。Son-O-Mermaid首先是为全地球地震（层析成像）应用而设计的。水听器阵列结构消除了非传播噪声并抑制了表面倍数。这种测深仪有助于以最大的精度确定远震波的传播时间。它还将为地球全球水深测量的高分辨率研究提供数据，因为Son-O-Mermaid是一个漂流仪器，表面洋流将是另一个副产品。由于可及性、物流和成本的原因，在海洋（不仅仅是海洋）进行的地球物理测量很少。虽然大陆上布满了精密的仪器，但如果需要在海洋中收集数据，除了访问海底或使用船上测量之外，几乎没有其他选择。对于全球地震学来说，海洋数据的缺乏是极其不利的，而对于地球科学的许多其他分支来说，海洋数据是必不可少的。物理、化学和生物海洋学都将得到低成本、自主和全球数据收集战略的服务。除水听器和测深器外，许多其他类型的仪器也可作为有效载荷。不用说，水听器可以探测到海洋中各种各样的声音信号，从冰川和冰原崩裂的声音，到鲸鱼和其他海洋动物的叫声，从遥远的、罕见的大地震的微弱隆隆声，到成群的山脊或变形断层活动。最后，当我们在寻找地球物理信号时，海洋噪声的研究是一门具有许多本质上有趣的科学问题以及实际和社会应用的学科。

A fully autonomous, long-lived marine geophysical instrument, the Son-O-Mermaid, was developed and with this grant, it will be tested at sea in three month-long deployments offshore the Bahamas, where deep water is easily accessible and ocean conditions generally favorable and well-characterized. Son-O-Mermaid is a freely drifting buoy that (1) derives energy from wave action, enough to power (2) a vertical array of hydrophones suspended from a compliant cable connected to a damping plate below the waves, (3) a full-ocean-depth echo sounder, (4) GPS for location and timing accuracy, (5) an IRIDIUM satellite communication unit for near real-time data transfer, and an (6) on-board digitizing and processing unit. No similar instrument exists. The predecessor instrument, MERMAID, differs in fundamental aspects from our Son-O-Mermaid. MERMAID is wholly lacking (1), (3) and the array aspect of (2). The Son-O-Mermaid capabilities (4)-(6) are always "on": the instrument is self-powered and as a whole never completely submerged at depth. The Son-O-Mermaid is to be deployed by untrained personnel from ships of opportunity, which gives it an extra advantage over conventional (e.g., ocean-bottom, tethered,moored) approaches. Son-O-Mermaid was first and foremost designed for whole-Earth seismological (tomographical) applications. The hydrophone array configuration eliminates non-propagating noise and suppresses surface multiples. The fathometer helps in determining the travel time of teleseismic waves with maximal accuracy. It will also deliver data for the high-resolution study of Earth's global bathymetry, and because Son-O-Mermaid is a drifting instrument, surface currents will be another byproduct.Geophysical measurements made in (not just of) the oceans are rare because of accessibility, logistics, and costs. While the continents are densely covered with sophisticated instrumentation, there are few alternatives, if the data need to be collected in the oceans, other than visiting the ocean floor or using shipboard measurements. For global seismology, the paucity of oceanic data is extremely detrimental, and to many other branches of Earth sciences, oceanic data are simply essential. Physical, chemical and biological oceanography will all be served by the availability of low-cost, autonomous, and global data collection strategies. Other than hydrophones and depth sounders, many other instrument types can be envisaged as payload. It also goes without saying that hydrophones will detect a whole range of acoustic signals in the oceans, from the crackling of glaciers and calving ice sheets to the calls of whales and other marine fauna, from the faint rumble of large, rare, and distant earthquakes to the swarms of ridge or transform-fault events. Lastly, while we are after geophysical signal, the study of acoustic noise in the ocean is a discipline with many intrinsically interesting scientific questions as well as practical and societal applications.