12 ISSN (Print): 1844-6116 ISSN (Online): 2501-8795 https://www. jmte.eu Journal of Marine Technology and Environment DOI: 10.53464/JMTE.02.2022.02 OCEANOGRAPHIC ENVIRONMENTAL ASSESSMENT USING UNDERWATER GLIDERS Laurențiu-Florin CONSTANTINOIU 1,2 , Luis QUARESMA 1 & Eugen RUSU 2 1 NATO Maritime Geospatial, Meteorological and Oceanographic Centre of Excellence, Lisbon, Portugal, e-mail address: florin.constantinoiu@mgeometoccoe.org 2 Galați “Dunărea de Jos” University, Faculty of Mechanical Engineering, 111 Domneasca Street, Galați, Romania, e-mail address: erusu@ugal.ro Abstract: REP(MUS) 21 is an annual exercise jointly organised by the Portuguese Navy, the University of Porto, NATO’s Centre for Maritime Research and Experimentation (CMRE) and the NATO Maritime Unmanned Systems Initiative. The exercise gives Allies and NATO partners a chance to field and evaluate new maritime technologies. A Rapid Environmental Assessment warfare group was formed using Maritime Unmanned Systems to perform an environmental assessment of this area, by collecting data from the upper ocean region (0- 200 m.), sea surface, littoral shallow waters, and river estuary. Underwater Gliders were used in the REPMUS21 exercise, brought by several partners, to conduct environmental observations from the underwater domain of the exercise’s Joint Operations Area (JOA). This paper focuses on the use of Seaxplorer underwater gliders to collect oceanographic data during the exercise, and the operational impact of using this knowledge to compile the Recognized Environmental Picture of the exercise area. Key words: environmental assessment, maritime unmanned systems, oceanography, REPMUS21 exercise, underwater glider 1. INTRODUCTION Gliders have a long history in collecting oceanographic data in different challenging environments, since the 90´s [1]. They have been used in military environmental data collection since they have long-endurance and can send rapidly in-theatre data. Geospatial, meteorological, and oceanographic knowledge is critical to optimize the employment of sensors, weapons, targeting, logistics, equipment and personnel and is a key decision superiority to enable safe, effective and successful operations. Operating in unfamiliar areas may require a dedicated mission to assess the environmental conditions of the TO and to provide NATO commanders with the opportunity to better plan, execute, support and sustain their operations. When these tasks are to be conducted in non-permissive theatres or to complement conventional military capabilities, the use of Maritime Unmanned Systems (MUS) becomes a game-changer. REP(MUS)21 stands for Robotic Experimentation and Prototyping Augmented by Maritime Unmanned Systems. The REP (MUS) exercise is an experimentation exercise for Maritime Unmanned Maritime Systems. It started in 2010, being organized by the Portuguese Navy and the Faculty of Engineering of the University of Porto (FEUP). This exercise has expanded in the last years capturing attention by many NATO Nations, companies, and Academia. The REP(MUS)21 exercise area was situated in a coastal region along the Portuguese continental shelf and inside the Sado estuary, limited from Sesimbra to Sines harbours, as seen in Figure 1. The main experimentation activities were executed around Troia peninsula and Sesimbra harbour, from deep ocean domains into very shallow coastal waters and inshore river areas. Figure 1 Area of the REP(MUS)21 exercise The main reason for assessing oceanographic parameters, from a military perspective, is to achieve a tactical advantage over one’s adversary by exploiting