Seafloor Observatory Network Research Articles

Research on an Extensible Monitoring System of a Seafloor Observatory Network in Laizhou Bay

An extensible remote monitoring system for a seafloor observatory network in Laizhou Bay was established to realize long-term, continuous and on-line monitoring for a marine ranching environment. This paper deals with data communication, device management and data quality control. A control model is introduced that is structured into four layers, enabling bidirectional information flow. Based on the control model, the standardized communication protocol and device object model-oriented dynamic management method are designed as plug-and-play, for data processing and control of a large number of devices. An improved data quality control method is proposed to reduce the data error rate. The monitoring system was developed based on socket network programming, MySQL database technologies and modular ideas. The seafloor observatory network was successfully deployed in Laizhou Bay marine ranching. The experimental results demonstrate that the monitoring system obtains better performance. The proposed algorithms can also be used in many other similar systems with adaptive requirements.

Design of deep-sea chemical data collector for the seafloor observatory network

This paper describes the design of a deep-sea chemical data collector for a seafloor observatory network. The control system of the data collector comprises the main control unit, energy supply distribution unit, serial port expansion unit, condition monitoring, power supply switching unit, and communication unit. The functions of the data collector include self-inspection, diagnosis, and isolation. It also transmits the collected data and the monitoring data in the data collector cabin to the shore station management system in real-time. The data is transmitted through the secondary junction box and the photoelectric composite cable. The data collector also includes optical dissolved oxygen, deep-sea methane, chlorophyll, turbidity, and colored dissolved organic matter (CDOM) sensors. In January 2017, the data collector integrated with domestic chemical sensors was used for the sea trial, in Jiaozhou Bay, Qingdao. The experimental results demonstrate the reliability of the system and the data quality of all chemical parameters.

Developing a power monitoring and protection system for the junction boxes of an experimental seafloor observatory network

A power monitoring and protection system based on an embedded processor was designed for the junction boxes (JBs) of an experimental seafloor observatory network in China. The system exhibits high reliability, fast response, and high real-time performance. A two-step power management method which uses metal-oxide-semiconductor field-effect transistors (MOSFETs) and a mechanical contactor in series was adopted to generate a reliable power switch, to limit surge currents and to facilitate automatic protection. Grounding fault diagnosis and environmental monitoring were conducted by designing a ground- ing fault detection circuit and by using selected sensors, respectively. The data collected from the JBs must be time-stamped for analysis and for correlation with other events and data. A highly precise system time, which is necessary for synchronizing the times within and across nodes, was generated through the IEEE 1588 (precision clock synchronization protocol for networked measurement and control systems) time synchronization method. In this method, time packets were exchanged between the grandmaster clock at the shore station and the slave clock module of the system. All the sections were verified individually in the laboratory prior to a sea trial. Finally, a subsystem for power monitoring and protection was integrated into the complete node system, installed in a frame, and deployed in the South China Sea. Results of the laboratory and sea trial experiments demonstrated that the developed system was effective, stable, reliable, and suitable for continuous deep-sea operation.

Development of a Plug-and-Play Monitoring System for Cabled Observatories in the East China Sea.

Seafloor observatories enable long term, continuous and multidisciplinary observations, promising major breakthroughs in marine environment research. The effort to remotely control in situ multidisciplinary equipment performing individual and cooperative tasks is both a challenge and a guarantee for the stable operations of functional observatories. With China starting to establish ocean observatory sensor networks, in this study we describe a monitoring system for cabled observatories in the East China Sea (ESOMS) that enables this effort in a plug and play way. An information oriented monitoring architecture for ESOMS was first introduced, derived from a layered control model for ocean observatory sensor network. The architecture contained three components and enabled bidirectional information flow of observation data and commands, based on which architecture components were designed to enable plug-and-play control within related model layers. A control method enabled by general junction box (GJB) and ocean sensor markup language (OSML) was thus proposed as the plug-and-play solution for implementing ESOMS. The GJB-OSML enabled control method (GOE Control Method) mainly actualized two processes, one of which was that the in situ GJB interfaced and represented every attached sensor as a Sensing Endpoint in the cabled observatory network. The other process was that the remote ESOMS utilized the same IP/Port related information modeled by OSML to create/operate a Function Node acted as agent of the in situ sensor. A case study for using ESOMS in the Xiaoqushan Seafloor Observatory was finally presented to prove its performance and applicability. Given this successful engineering trial, the ESOMS design and implementation could be applicable and beneficial for similar efforts in future construction of seafloor observatory network both at home and abroad.

Information Fusion of Seafloor Observatory Network Based on Kalman Filtering

The necessity and advantages of the multi-sensor’s application in information fusion is analyzed on the basis of that multi-sensor information fusion technology has been widely applied in the monitoring and control system of seafloor observatory network. and the structural model of fusion system based on the distributed filtering scheme is presented. Decentralized kalman filtering is proposed to solve the fusion structure model of the system, and the information fusion algorithm based on kalman filtering is discussed in depth. And the research findings of Kalman filtering in information fusion are tested with Mat lab. Simulation shows that system design can integrate the lowest layer of sensor signals quickly and accurately, giving helps for decision making.

Reliability Analysis and Optimization of Constant Current Remote Power Feeding System of Seafloor Observatory Network

Study on the deterioration of the constant current remote feeding system throughout the life of the structure is always one of the most important issues in seafloor observatory network reliability engineering. Relationship between current-to-current convertor subsystem and amount of loads in branch line is described by introducing failure rate factor. Multistate reliability model of remote power feeding system has been set up and solved by genetic algorithms. Simulation results show that as the load configuration in trunk line and branch line changing, there exists best combination maximizes the system reliability, besides, appropriate increasing amount of loads in branch line can optimize the preventive strategy.

The Reliability Design and Analysis of Series Constant Current Remote Power Feeding System of Seafloor Observatory Network

The paper makes a deep analysis of the series constant current remote power feeding system which is used in seafloor observatory network. The reliability design and allocation scheme used to minimize the total cost of the system in certain condition is accomplished, and the nodes power feeding reliabilities are calculated. The analysis shows that series system can provide a reference solution for seafloor observatory network construction in our country.

IEEE 1588 based time synchronization system for a seafloor observatory network

An IEEE 1588 based application scheme was proposed to achieve accurate time synchronization for a deep seafloor observatory network based on the communication topological structure of the Zhejiang University Experimental and Research Observatory. The principles of the network time protocol (NTP) and precision time protocol (PTP) were analyzed. The framework for time synchronization of the shore station, undersea junction box layer, and submarine science instrument layer was designed. NTP and PTP network signals were decoded by a PTP master clock on a shore station that receives signals from the Global Positioning System and the BeiDou Navigation Satellite System as reference time sources. These signals were remotely transmitted by a subsea optical-electrical composite cable through an Ethernet passive optical network. Accurate time was determined by time synchronization devices in each layer. Synchronization monitoring experiments performed within a laboratory environment indicated that the proposed system is valid and has the potential to realize microsecond accuracy to satisfy the time synchronization requirements of a high-precision seafloor observatory network.

Branch Unit for Seafloor Observatory Network

One key issue of seafloor observatory network is to ensure that the whole system operates normally when some equipment failure exists. Branch Unit can cut off the connection between the failure parts and the backbone network automatically and protect other equipment of the network from the impact of equipment failure. This paper proposes a design of the Branch Unit. The Branch Unit uses zener diode to provide power for the control circuits and constructs DWDM system with the help of the OADM. One Branch Unit model was built in this paper. Experiments verify the principle and functions of the Branch Unit and prove the feasibility of the design. The design provides a reference for the realization of the seafloor observatory network.

Changes in 63 Hz third-octave band sound levels over 42 months recorded at four deep-ocean observatories

The growing scientific and societal concerns about the effects of underwater sound on marine ecosystems have been recently recognised through the introduction of several international initiatives, like the International Quiet Ocean Experiment, aimed at measuring the environmental impact of ocean noise on large spatial and temporal scales. From a regulatory perspective, the European Marine Strategy Framework Directive includes noise (and other forms of energy) as one of eleven descriptors of good environmental status of Europe's seas. The directive requires member states to monitor trends in annually averaged sound. The Laboratory of Applied Bioacoustics has developed a software package that measures sound levels and monitors acoustic sources in real-time; this software was used for the LIDO project (www.listentothedeep.com), which originated from the European Seafloor Observatory Network of Excellence (ESONET-NoE; www.esonet-noe.org). The system is currently operating worldwide from several wired and radio-linked observatories. The CTBTO (Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization) has made available years of data from hydroacoustic stations to look for ambient sound trends and to detect cetacean presence. Here, we present the analysis of four CTBTO platforms (located in the Pacific, Atlantic and Indian oceans), covering 42months of data, intended to detect annual and monthly changes or trends in the ambient sound levels.

Design of Prototype System for Seafloor Observatory Network

Developing the seafloor observatory network(SONet) is very significant for the human to explore the ocean resources. The information system of seafloor observatory network provides a platform for scientists to research the seafloor activities, which is a kind of open and complex system referring to diverse engineering and disciplines. The data acquiring, storing and management of the observatory instruments are the major parts of information integration. A prototype system based on the SOA(Service-oriented Architecture) is designed to manage information and knowledge in SONet. The SOA architecture, interface and device encoding mechanism are presented. Benefit from this, construction and application of the system can provide a uniform information and knowledge platform in the ocean field.

Records of the tsunami induced by the 2010 Chilean earthquake from Xiaoqushan seafloor observatory in the East China Sea

Sea-level variation can be induced by periodic tides, stochastic wind, air pressure, and swell. Larger sea-level variation has the potential to cause coastal disasters. In this paper, real-time continuous data obtained by the Xiaoqushan seafloor observatory in the East China Sea were analyzed employing frequency power spectral and tidal harmonic methods to extract the major components and periodicities of sea-level change. The sea-level anomaly (sla) was calculated by subtracting the tidal components from the observed sea level data. In the study period, the correlation between sla and the local north-south wind speed was high with a correlation coefficient of 0.65 at the 95% confidence level. The local wind-induced sea-level anomaly (slawind) was therefore computed through linear fitting. Although slawind is one of the main components of sla, the residual sea-level anomaly (slaresidual) obtained by subtracting slawind from sla is not zero, suggesting that there are other factors besides wind. Detailed analysis of the sea-level data at the time of the 8.8-magnitude Chilean earthquake on February 27, 2010 showed a peak slaresidual value of 0.48 m at around 15:00 on February 28, which was highly coincident with the tsunami arrival time forecast by the Pacific Tsunami Warning Center. The peak slaresidual event is therefore linked with the tsunami induced by the 2010 Chilean earthquake. This is the first time that a tsunami has been detected using real-time continuous data recorded by a seafloor observatory in the sea off China. Such observations are expected to improve tsunami forecast models and promote the development of a tsunami warning system and a seafloor observatory network in the East China Sea.

Space–time and hybrid algorithms for the passive acoustic localisation of sperm whales and vessels

In the frame of the European Sea-floor Observatory Network (ESONET) and in preparation of the Demonstration Mission Listening to the Deep-Ocean Environment (LIDO) algorithms for the automated real-time detection, classification and localisation of cetaceans have been developed. Such Passive Acoustic Monitoring techniques have the potential to play a key role in cetaceans’ conservation for they allow a non-invasive study of their behaviour, a better knowledge of their population dynamics, and a better understanding of their dynamic relationship with their environment. This paper investigates the development of efficient and accurate techniques to be used as the basis of a localisation module for an automated real-time Passive Acoustic Monitoring system. An opportunity to assess the capabilities of the developed localisation modules was given by recordings collected with a bottom-mounted (around 2080 m depth) tetrahedral compact hydrophone array located offshore the port of Catania (Sicily) during the NEMO-ONDE campaign in the years 2005–2006 by INFN and CIBRA [2]. A well-known class of methods for acoustic source localisation is based on time differences of arrival (TDOA). Its capabilities have shown to be useful even in adverse situations (i.e., few sensors, high noise levels and/or poor calibration). A second class of methods, the space–time methods, originated in underwater applications such as sonar but reached its most significant achievements over the last 20 years in digital communications with recent progress in the treatment of broadband signals. These developments are here revisited under the scope of the localisation and tracking of cetacean vocalisations. Various broadband space–time methods were implemented and allowed to map the sound radiated during the detected clicks and to consequently localise both sperm whales and vessels. Hybrid methods were also developed which improved the robustness of space–time methods to noise and reverberation and reduced processing time. In most cases, the small variance obtained for these estimates lessened the necessity of additional statistical clustering. Even though not independently confirmed by sightings, the tracks derived in the proposed frame can be considered to be consistent with the known movements of sperm whales and vessels.

A conceptual design of high density real time seafloor observatory network.

A conceptual design of high density real time seafloor observatory network.

NEMO-SN-1 the first “real-time” seafloor observatory of ESONET

The fruitful collaboration between Italian Research Institutions, particularly Istituto Nazionale di Fisica Nucleare (INFN) and Istituto Nazionale di Geofisica e Vulcanologia (INGV) together with Marine Engineering Companies, led to the development of NEMO-SN-1, the first European cabled seafloor multiparameter observatory. This observatory, deployed at 2060m w.d. about 12 miles off-shore the Eastern coasts of Sicily (Southern Italy), is in real-time acquisition since January 2005 and addressed to different set of measurements: geophysical and oceanographic. In particular the SN-1 seismological data are integrated in the INGV land-based national seismic network, and they arrive in real-time to the Operative Centre in Rome. In the European Commission (EC) European Seafloor Observatory NETwork (ESONET) project, in connection to the Global Monitoring for Environment and Security (GMES) action plan, the NEMO-SN-1 site has been proposed as an European key area, both for its intrinsic importance for geo-hazards and for the availability of infrastructure as a stepwise development in GMES program. Presently, NEMO-SN-1 is the only ESONET site operative. The paper gives a description of SN-1 observatory with examples of data.