Sea Technology

NOV 2018

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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Page 18 of 52

18 ST | November 2018 information and the ability to make multiple SV profiles at several locations autonomously. By clever data com- pression techniques, ecoSUB can deliver a full sound ve- locity downcast with speed of sound, depth and latitude/ longitude every meter through 290 m in a single Iridium short-burst data (SBD) message before traveling to a new location to repeat the process. This can be extended to 500 m with up- and downcasts using multiple SBD mes- sages or adjusting the interval from less than 1 m to more than 1 m as required in the mission plan. This provides decision makers with a very detailed 3D map of the un- derwater acoustic environment over a wide area in near real time and in advance of the host vessels arrival at the location. Making an accurate physical measurement of sound velocity reduces errors inherent in calculating sound speed using multiple sensors each with its own error band. The Valeport time-of-flight SV sensor provides: accu- racy of ±0.02 m/s (total error budget); precision (peak-to- peak noise) of ±0.002 m/s; operating range of 1,375 to 1,900 m/s (covering all environments from freshwater to the Dead Sea and the Marianas Trench); and data rates up to 60 Hz (instrument dependent). Typically, ecoSUB sensors and electronics are locat- ed within the free-flooding nose cone of the vehicle. To accommodate the Valeport sensor, a new ecoSUB nose cone was required. Valeport provided pressure-tolerant electronics that could be fitted within the nose cone and perform at pressures of 50 bar or more. In addition, Valeport was asked to provide a sensor with the shortest possible path length to minimize the drag experienced by the vehicle while providing the re- quired exposure for the sensor to maintain performance, as well as making the electronics package as close to naturally buoyant as possible. An advantage of the ecoSUB moving mass system is the steep dive angle. When diving steeply, ecoSUB nat- urally spirals, keeping the footprint of the dive extremely tight. This can be enhanced further by applying full right or left rudder as part of the profile dive behavior. In the Field The first batch of five vehicles were produced in May 2018 and subjected to extensive sea trials with remark- able results before being supplied to the customer. At the time of writing, four vehicles are being prepared for de- ployment on an exercise in the northern North Sea. The subs will be piloted remotely, using the Iridium channel that, with the aid of a specially designed C3 base station, allows over-the-horizon communications with the subs in an internet-denied environment. New missions or al- terations to existing missions can be uploaded on the fly when vehicles are on the surface. Working with stakeholders, particularly in the ener- gy and defense sectors, there is a growing understanding that in some circumstances, information can be more valuable than data. This often means that decision mak- ers need to be provided with preprocessed information rather than complex data sets to allow them to make speedy yet educated decisions. An example of this is in anti-submarine warfare (ASW), where knowledge of the depth of the temperature inversion layer is required. By processing the sound velocity data on board ecoSUB and simply sending a subset of the data located around the inversion depth, or even a concise report along the lines of "thermocline at 40.55 m latitude 0° 00" 0.000" longitude 0° 00" 0.000"," decision makers are not over- whelmed by complex or lengthy data sets requiring in- terpretation. Raw data are always available and stored locally for use offline as required. Mindful of the value of the data collected, facilities have been incorporated for erasure of the data remotely if necessary. ecoSUB is currently available in two variants: the micro (µ) 500 m rated and milli (m) 1 m in length and 500 m or 2,500 m rated. Valeport has provided special- ly commissioned versions of its Hyperion fluorometer system with fast time constant temperature sensor and echosounder for use specifically on ecoSUB vehicles. ecoSUB Robotics is now developing a range of payload configurations and firmware modules suitable for com- bat hydrography and other defense applications. ST Terry Sloane began his career in 1975 as an elec- tronics engineer with Marconi Space & Defence Systems working on torpedoes and later became technical director at NBA Environmental Systems. In 1994, he co-founded Hydrosphere UK Ltd., and in 2003 he formed Planet Ocean Ltd. Sloane established ecoSUB Robotics Ltd. in 2016 to de- velop AUVs, designed in collaboration with the MARS group at the NOC Southampton. ecoSUB-µ5 SVP.

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