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ALSEAMAR was taking part, for 3 weeks, in the ‘REPMUS 2022’ and ‘DYNAMIC MESSENGER’ exercises organized by the Portuguese Navy and NATO.
‘REPMUS’, which stands for Robotic Experimentation and Prototyping with Maritime Unmanned System, is a Portuguese Navy-led exercise focusing on capabilities development and interoperability. This year’s edition took place from 12th to 22nd of September 2022 in the Portuguese Naval Base of Troia (south of Lisbon), in the same location where the exercise has been held since 2004. 2000 participants from 120 different entities participated in the exercise, in which NATO Maritime Unmanned Systems Initiative (MUSI) has been playing a growing role since 2019.
‘DYNAMIC MESSENGER’ (DYMS) is the first of an annual series of experimentation exercises, under the joint ownership of the NATO Maritime Commander (MARCOM) and the Allied Command Transformation (ACT). 2022 was the first iteration of this exercise, which is designed to allow large-scale OPEX where NATO operational communities (Nations and NATO entities) work together with Industry and Academia to develop operational concepts and doctrine and promote integration of Maritime Unmanned Systems (MUS) into NATO operations utilizing the NATO Standing Maritime Forces.
SeaExplorer long-range UUVs deployed for the exercises
The SeaExplorer underwater glider is a small sized, persistent and very long range UUV (Unmanned Underwater Vehicle), capable to acquire data for months at sea while operating on a stealth mode, thanks to its silent buoyancy engine which uses gravity to propel the vehicle. The glider moves forward going up and down through the water column, from the surface down to 1000m depth, allowing data acquisition in 4D. Moreover, as the glider is not propelled by a thruster, it is an extremely quiet platform and it’s very well suited for acoustic data acquisition and/or acoustic detection.
Three SeaExplorer gliders were planned to be deployed during the exercises: two operated by the French Minister of Defense (DGA – Direction Générale de l’Armement), and one by the Portuguese Navy (Marinha Portuguesa). Due to difficulties of some other participating assets, a fourth SeaExplorer was deployed on request from NATO Maritime GEOMETOC Centre of Excellence to further increase the spatial coverage.
The four vehicles cumulated a total of 67 days at sea, covering a total distance of 1,771 km and performing 1,347 dives for data acquisition over the 21days of the two exercises. With a single battery charge before the beginning of the exercise, the vehicles were retrieved at sea with still significant remaining energy that would allow to ensure longer operations at sea.
| Asset | Distance covered | Days at sea | Number of data profiles acquired |
| SEA037 (FR01) | 600 km | 21 days | 521 |
| SEA006 (FR02) | 497 km | 21 days | 259 |
| SEA054 (PT01) | 392 km | 12 days | 354 |
| SEA050 (PT17) | 282 km | 13 days | 213 |
| Total | 1,771 km | 67 days | 1,347 |
Supervision of fleets of UUVs
The fleet of four SeaExplorer was supervised by ALSEAMAR’s GLIMPSE mission planning and supervision interface. The four units perfectly followed their planned trajectories (on a 50x50km area) despite the water currents present on the area.
The GLIMPSE interface allowed a limited team to supervise this critical mission and was displayed in the Exercise Control Room. The position of the vehicles was also displayed on NATO Maritime GEOMETOC Centre of Excellence centralized interface.
SeaExplorer UUV for REA and ASW
The SeaExplorer underwater glider mission was supervised by NATO’s Maritime GEOMETOC Centre of Excellence, responsible for the Rapid Environmental Assessment (REA) of the area. The four vehicles of the fleet were equipped with both a CTD sensor (conductivity, temperature and depth) and an AGLIMMS 8-hydrophones acoustic array.
This allowed to provide real time assessment of sonar propagation, with each glider sending sound velocity profiles at each surfacing, as shown hereunder. The image shows in color the speed of sound, varying with depth (y-axis) and distance (x-axis). A minimal celerity zone can be spotted around 300m of depth in the image and a profile acting as an acoustic propagating channel at such depth. This data was available in real-time thanks to the satellite communication system of the vehicles.
The capacity to perform embedded real-time calculation of the noise spectrum was also demonstrated, as shown on the following picture. The AGLIMMS 8-channel acoustic payload is indeed capable to assess the ambient noise directivity and to compute its spectrum and send by satellite communication the levels of noise for different frequencies calculated every minute of navigation. The below image (left picture) shows noise levels for low, mid, and high frequencies, displayed in real-time on the supervision interface after satellite transmission. Sonar propagation assessment was performed during the mission using the data retrieved on shore, using specific processing tools developed by ALSEAMAR, as shown on the second image (right picture).
This exercise allowed ALSEAMAR to demonstrate the performance and maturity of the SeaExplorer UUV for Defense application. A total of eight underwater gliders from different Navies were planned to be deployed, including three SeaExplorer. Following failures of other assets and the introduction of a fourth SeaExplorer to compensate, the mission ended with a total of seven gliders deployed, including four SeaExplorer. This shows how challenging those type of missions can be, and how reliable is the SeaExplorer technology.
The exercise also showed the interest of ALSEAMAR’s strategy to focus into the whole System by designing not only the vehicle, but also its payload, automated data processing and supervision infrastructure; instead of focusing only on the vehicle.
The SeaExplorer System also demonstrated that it is fully operational for any nation for REA, ACOUSTINT, and ASW-helping missions.
To learn more about the SeaExplorer, visit ALSEAMAR during Euronaval 2022 on stand G21. A SeaExplorer will also be showcased on the French Ministry of Armed Forces booth.
