Issue 55 Uncrewed Systems Technology Apr/May 2024 Sellafield’s UAV equipment l Applied EV Blanc Robot l Battery tech l Robotican’s Goshawk l UGVs l UAVHE RW1 rotary l Roboat UVD l Autopilots l Arkeocean UVD l UMEX 2024 l CycloTech UVD

Arkeocean’s Inca & Maya anti-sub warfare UUVs | In operation receiving (Rx) phased array, which gives the relative bearing of incident acoustic signals, and a transmitter (Tx) used for the emission of acoustic positioning signals. The SEAKER on each Inca codes its vehicle’s heading using time-shift keying at each acoustic transmission, which the Maya then receives and decodes to easily align itself with the Inca for mechanically docking with it. After docking, the Mayas download the survey data (with each Maya using a very short-distance wi-fi connection to its Inca) and transmit it to the C2 centre via wi-fi after surfacing, doubling as LBL beacons during their upload time on the surface. Beamforming The ability to localise the Incas with 1.5 m accuracy is a critical part of the use-case. To carry out beamforming (a method that enhances the signal-tonoise ratio, mitigates interference and achieves very efficient antenna gain) the position of the antenna’s receiving nodes must be accurate in metres to one-tenth of the wavelength of the higher end of the band in hertz. “As we have a 15 m wavelength for the 100 Hz end of the ULF band, keeping the nodes positioned to 1.5 m accuracy ensures the swarming antenna can do beamforming,” Brizard explains. The Mayas transfer each Inca’s data to the C2 centre about once per hour on average, through which the C2 centre can perform sonar processing and beamforming. Following that, the detection, localisation and in some cases even classification of remote threats can be carried out. Post-mission Recovery of all the AUVs at the end of their mission is rapidly performed via a large, metal basket, lowered by crane into the water, with an acoustic beacon whose signal the Incas and Mayas can detect. This signal activates an automated homing function, compelling the micro-AUVs to swim into the basket. Once the crew topside are confident that the AUVs have all returned, they can raise the basket and lift then all onto the deck. “The first thing we do after recovering the AUVs is quality control of the survey data. Each Inca carries a ULF recorder, which compiles all telemetry over the course of its mission to exact fidelity, which is important, not only to account for inertial drift but also in the event that some data could have been corrupted while uploading from an Inca to a Maya, or from a Maya to the C2 centre,” Brizard says. “So, the recorder ensures data redundancy, such that we can ‘repair’ any flaws and faults within. After working for Thales, I spent some time in geophysics, and in that industry there’s only one thing geophysicists care about: the quality of the survey data and ensuring the beamforming will provide the required antenna gain to ascertain and analyse the number and type of submarine, or other remote subsea threats that were detected.” Future targets Arkeocean is continuing to optimise and modify its AUVs for different operational models, including versions that will leverage loitering modes for Incas in the column of water or sitting on the seafloor at low power for long periods of time. In both cases, they will surface for data transfer upon detecting a threat. This is currently being explored through the company’s LELANTOS solution, tested at sea by the French Navy. Additional areas of interest include acoustic modems for UUV-to-UUV communications in real time, as well as the means by which AI behaviours can be installed in the micro-AUVs (particularly for functions such as realtime identification of complex acoustic signatures and enhancing detection probabilities) without driving up their cost and consuming their energy stores inordinately fast. Arkeocean aims to manufacture and deliver 25 AUVs by the end of Q1 2024, with further plans to ramp up production to several hundred units by the end of 2025, with its customers largely composed of defence organisations that cannot be publicly disclosed as of writing. To achieve these targets, Arkeocean is focused on hiring new engineers and other team members for its facilities in Brittany, both to increase manufacturing throughput and to design its nextgeneration swarming vehicles. One of these is a AUV larger than Maya and Inca, which will be capable of operating down to 3000 m below the ocean surface. 103 Uncrewed Systems Technology | April/May 2024 Inca Micro-AUV Length: 800 mm Weight in air: 17 kg Maximum speed: 5 knots Maximum operating depth: 300 m Maximum range (at 3 knots): 20 km Battery energy: 600 Wh Maya Micro-AUV Dimensions: 570 x 370 x 370 mm Weight in air: 8 kg Maximum speed: 3 knots Maximum operating depth: 300 m Communication modes: 433 MHz, 2.4 GHz, 4G, Iridium (18 MHz optional) Some key suppliers: Thrusters: Blue Robotics ESCs: Aikon Electronics IMUs: SBG Systems DVLs: Water Linked Argos native positioning beacons: Kinéis Satcom modems: Iridium Key specifications