Feature ArticlesOBSEA: an Expandable Seafloor Observatory
By Antoni Mánuel-Lázaro
Expandable Seafloor Observatory Project Manager
Joaquín del Río Assistant Professor
Remote Acquisition and Data Processing Systems
Universitat Politécnica de Catalunya
In oceanographic observation, higher resolution, a larger volume of information and longer data series are becoming increasingly important. In some applications, traditional observation systems (such as autonomous oceanographic buoys and measurements taken from oceanographic ships) present serious disadvantages regarding costs, volume and delay of data, or battery autonomy. The new cabled underwater observatories, on the other hand, are modular, flexible and adaptable to different uses and specifications.
The Expandable Seafloor Observatory (OBSEA) project is a collaboration between the Consejo Superior de Investigaciones Científicas (CSIC) and the Universitat Politécnica de Catalunya (UPC) to design and develop a seafloor observatory situated off the Vilanova i la Geltrú coast of Spain in the Colls Miralpeix marine reserve.
OBSEA is a multiparameter laboratory for oceanographic studies integrated into the coastal zone and a test site for marine equipment included in the European Seafloor Observation Network (ESONET).
The OBSEA infrastructure consists of two main installations: the shore station and the subsea station. The subsea station has all of the oceanographic instruments and related electronics for power supply, communications and control. The management servers, which are in charge of status monitoring and data collection, are located at the shore station. These data servers continually store information and give controlled access to the scientific community.
The main objective of the OBSEA project is to provide a test bed for the development of oceanographic instrumentation and, at the same time, provide valuable information to the scientific community. This observatory provides real-time data for marine observations and maintains a database of historical values.
All of the instruments are transparently accessible to users through a TCP/IP connection.
The OBSEA observatory is equipped with three instruments: an underwater camera providing real-time images from the seafloor, which is useful for monitoring marine organisms as well as for security surveillance; a broadband hydrophone for acoustic monitoring, condition metering and background noise recording; and a mooring conductivity, temperature and depth sensor, which provides important information on long-term salinity and thermal variations as well as tidal evolution. OBSEA is not limited to these three sensors, however, as it has free ports that can be used to connect any type of oceanographic instrument. In fact, an acoustic Doppler current profiler has been installed on OBSEA for climate studies in Colls Miralpeix's integrated coastal zone.
The OBSEA observatory was installed four kilometers from the Vilanova coast at a 20-meter depth for easy access. The main components of the underwater station have been designed to withstand 30 bar of water pressure and have been tested at 20 bar inside the hyperbaric chamber facility at the Remote Acquisition and Data Processing Systems (SARTI) laboratories.
Diagram of the OBSEA network.
Power Supply, Data Management
When planning network infrastructure, it is always advisable to develop a proper Ethernet network architecture that will provide a good communication medium for maintaining security. In the OBSEA network, external access to the instruments is restricted, and only acquired data is forwarded.
One server device is designated for each provided service. Server 1 is used for services related to the subsea webcam video recording and image provider (acquisition from webcam, video frame storage, video server, etc.). Server 2 implements all of the services related to the hydrophone: data reception, sound processing and packet forwarding to external users. Server 3 implements the network management and error monitoring with a simple network management protocol server. Finally, Server 4 stores the sensor information in a database and is in charge of extended services.
The current design supports as many as eight wet-mateable external instruments, each powered by up to three amperes at 12 or 48 volts and with a 10/100-megabit-per-second Ethernet connection. The trunk line to the shore is a 1+1 optical connection at one gigabit per second.
All of this equipment is placed in the stable, 4.6-square-meter stainless steel structure designed to protect all instrumentation from unauthorized manipulation. The system is powered from the shore station with a 3.6-kilowatt power supply delivering as many as 320 volts and 11 amperes direct current, but there are plans to incorporate a 1,000-volt power supply in the future, delivering more power and allowing for longer cables.
Design Problems and Solutions
During the design process of the OBSEA project, a number of problems needed to be addressed. One was the necessity of using feeding equipment that worked continuously and was installed some kilometers away from the control center. Therefore, the system was designed to detect the observatory's consumption variations and respond automatically (without action from an operator). Furthermore, since complementary sensors can be later added to the observatory, the power supply needed to have a wide enough consumption margin to meet higher future energy demands. Finally, to enable monitoring of the process, periodic reports and incident signaling were needed.
To meet these requirements, the whole system was designed around a programmable logic controller (PLC), which analyzes observatory consumption using the data obtained by current and voltage sensors. Consequently, it activates the necessary number of converter switches. In typical conditions, the acquisition system works with only four converter switches, but as many as 12 units have been installed to respond to possible consumption peaks or failures. The main elements of the system are the Omron Corp. (Kyoto, Japan) CP1L M30DR-A PLC, the 12 Mean Well Enterprises Co. Ltd. (Taipei, Taiwan) SP-300-27 converter switches that supply 27 volts direct current each and the CPM1A-MAD01 analog module PLC from Omron, which deals with the data acquired by the sensors. All are fed directly from the electrical grid.
An agreement for data sharing has been made with the Catalonian Meteorological Institute. In addition, some research projects have been done in parallel using the OBSEA infrastructure, such as boron measurements for water desalination studies.
One of the objectives of the ESONET network has been noise monitoring to investigate the noise level produced around European coastlines and its environmental impact (especially the impact on cetaceans). The OBSEA broadband hydrophone is used in the Listening to the Deep Ocean Environment ESONET project.
The identification of species and the estimation of their biomasses and associated behavioral rhythms is becoming increasingly important for fishery management and biodiversity estimation in the continental margin and deep-sea areas.
In the past two decades, the number of submarine video stations has increased, along with socioeconomic interest in ocean exploration. In this context, expandable subsea stations, such as SARTI-UPC's western Mediterranean OBSEA, were installed at different depths to measure several marine parameters, including taking videos. Accordingly, the Marine Sciences Institute of the CSIC has elaborated a novel morphometry-based protocol for automated video-image analysis of data from the OBSEA camera. This approach accomplishes species identification with Fourier descriptors and Standard K-Nearest Neighbor analyses on their outlines and performs animal movement tracking (by frame subtraction), both in the demersal and pelagic realms.
Conclusions With OBSEA, real-time observation of multiple parameters in the marine environment is achieved. The main advantages of having a cabled observatory are providing continuous power to scientific instruments and having a high-bandwidth communication link.
Before the development of seafloor observatories, most autonomous stations were battery powered and stored data locally. This meant that they had to be periodically visited to change batteries and retrieve data.
The OBSEA project is directly connected to a ground station by cable, therefore it does not have these drawbacks.
The OBSEA station is a low-cost observatory, costing '700,000 to build, yet it is very capable of enabling the investigation and development of marine technology.
The observatory's received data are being stored for future studies and also being transmitted in real time to interested customers who have investigation projects related to ocean observation and climate change.
OBSEA is funded by the Spanish Ministry of Education and Science under a project titled 'Interoperabilidad en Redes de Sensores Marinos y Ambientales' (CTM2008-04517/MAR). The authors acknowledge the support of Jordi Sorribas and Jacopo Aguzzi, members of the research team at CSIC's Marine Technology Unit, and Javier Cadena, Carla Artero, Pep Santamaria, Norman Carreras, Daniel Toma and Shahram Shariat-Panahi of SARTI. Subsea pictures were provided by Ramon Margalef of STECMA (Sabadell, Spain).
For a full list of references, please contact Antoni Mánuel-Lázaro at firstname.lastname@example.org.
Antoni Mánuel-Lázaro received his bachelor's degree in 1980 and his Ph.D. in telecommunication engineering in 1996 from the Technical University of Catalonia. He is an associate professor with the department of electronic engineering at Universitat Politécnica de Catalunya and is currently the director of the Technological Development Center of the Remote Acquisition and Data Processing Systems' Marine Technology Associated Unit.
Marc Nogueras received his Master of Science in telecommunication engineering in 2003 from the Technical University of Catalonia, Spain. After three years designing and commissioning fiber optic networks for electrical utilities, in 2006 he joined the Remote Acquisition and Data Processing Systems research group and is currently the Expandable Seafloor Observatory project manager.
Joaquín del Río received his Bachelor of Science in telecommunications engineering in 1999 and his Master of Science in electronic engineering in 2002 from the Technical University of Catalonia, Spain. He is a member of the Remote Acquisition and Data Processing Systems research group and is currently working on the execution of signal processing algorithms on programmable hardware for smart sensor design.