Page 50: of Marine Technology Magazine (May 2014)

AUV Operations

Read this page in Pdf, Flash or Html5 edition of May 2014 Marine Technology Magazine

Products Delegates from the French Research Institute for Exploration of the Sea (Ifremer) visited the Kongsberg Mari- time Subsea headquarters in Horten, Norway late December 2013 for the Factory Acceptance Test of its second Simrad ME70 scientiÞ c multibeam echosounder. Ifremer acquired the multibeam echo sounder Ð the Simrad ME70 delivered as part of the mid-life reÞ t of the LÕEurope Research Vessel Ð to strengthen its work in the Mediter- ranean Sea. Sea trials on the reÞ t ves- sel are planned for March 2014.The delivery completes the already installed Simrad EK60 scientiÞ c sin- gle beam echosounder system to cre-ate a standardized package that com-bines quantitative single beam and multibeam systems for vessels that carry out biological surveys. Ifremer has also chosen the ME70 bathymet-ric module, enabling the ME70 to per- form seabed mapping according to in-ternational standards while at the same time doing ecosystem surveys of the water column. The Simrad ME70 has a built in cali- bration functionality in the software, made possible because the ME70 utilizes split beams in all beams. A calibration sphere with known target strength is used to calibrate the entire system, allowing the user to obtain ab- solute backscatter values from ecosys- tem components such as plankton, Þ sh or bottom habitat. Calibrated back-scatter data are also relevant for bot- tom classiÞ cation, as backscatter lev- els can be compared on the same scale.Also the Simrad ME70 offers its fully populated element array in both alongship and athwartship direction. A total of 800 individual elements in the transducer are used to form up to 45 split beams spread out in a fan in the athwartship direction. As individual beams are formed in both transmis-sion and reception, two way side lobe suppression give side lobe levels lower than -35 dB. Coupled with Frequency Rotated Directional Transmission (FRDT), where operating frequency is shifted between the beams to avoid interleakage, the ME70 is designed to allow the user to measure weak targets close to strong ones, which is essen-tial when your goal is to map the entire marine ecosystem. ÒThe ME70 has added another di-mension to our biological surveys on board the R/V Thalassa as it addresses some of the physical shortcomings of quantitative single beam echo sound- ers such as low resolution and sam- pling volume. It has been many years since we started using the ME70 on Thalassa, but we have now come to a point where we standardize the com-bination of quantitative multibeam and multifrequency single beam systems on board our vessels that carry out biological survey and research,Ó adds Laurent Berger, Þ shery acoustician at Ifremer. Ifremer Receives ScientiÞ c Multibeam May 201450 MTRMTR #4 (50-64).indd 50MTR #4 (50-64).indd 505/12/2014 2:37:50 PM5/12/2014 2:37:50 PM

Marine Technology

Marine Technology Reporter is the world's largest audited subsea industry publication serving the offshore energy, subsea defense and scientific communities.