# The POSEIDON Ocean Observing System: Technological Development and Challenges
## 6 Summary and Perspectives  
The POSEIDON Marine Forecasting and Information System for the Greek Seas is a state-of-the-art, widely recognizable operational system. The system consists of the following components: The observing system, which is comprises a network of different observing platforms; The forecasting system, which consists of a suite of numerical models that provide daily basis atmospheric, wave, hydrodynamic and ecosystem forecasts for the next five days; The marine technology unit that provides the engineering and technical backbone to operate the observing facilities, while it is also responsible for the testing and integration of new technologies in the monitoring platforms; The data management and dissemination unit, which collects and processes the data from the monitoring network and distributes the observing and forecasting products to the linked European Infrastructures and to the public. The scientific objectives of POSEIDON are to provide knowledge and support in the study of the ocean mechanisms and their variability, as well as to address the sensitivity of marine ecosystem and biodiversity to combined natural forcing factors and anthropogenic pressures. In addition to the scientific contribution and driven by societal needs, the system provides products such as quality and validated forecasts of the marine environment, proxy estimations, hazard mapping, and warning systems. As a part of the national scale RI: HIMIOFoTS, the POSEIDON system is actively contributing to integratingthe Greek observing capacity in the ocean-coastal-inland nexus under a unified structure with a common strategy and priority setting based on the national requirements and the European and international landscape. The long-term goals in the POSEIDON technology development are driven by setting ambitious targets such as strengthening the high-resolution surface and mid-layer data and products, operating in deeper regions and introducing new variables. These targets will be achieved by (a) coupling technology and science beyond the state of the art in order to actively participate in the technological development and innovating solutions, (b) investing in personnel and facilities for operating, testing and validating sensors and equipment (pressure chambers and experimental tanks, testing equipment and reference standards) and (c) networking on the international and national levels in order to make the POSEIDON not only the most advanced monitoring, forecasting and information system in the East Med, but also a leader in marine technology development. New monitoring technologies for pollutants and eDNA, advanced data analysis techniques, high accuracy instrumentation for eutrophication and acidification studies, coupled monitoring schemes with aerial, surface and underwater drones, animal-borne scientific payloads, cost effective citizen operated sensors and platforms, UIoT and cloud architectures in combination with AI data analysis and advanced modelling tools are under development and will be eventually integrated in the marine research observatories, leading to a new era of ocean exploration and scientific discoveries. Conceptualization, M.N., L.P. and G.P. ; investigation, L.P., G.P., G.K., C.F. and D.B. ; resources, D.B., C.F., P.P., E.B., M.S. and M.N. ; data curation C.F., D.B., P.M.S., M.P., E.B., S.C., D.K., N.Z., S.M., D.D., A.M.(Antigoni Moira), A.M. (Aspasia Marvoudi), G.A., A.P., C.O., N.S. and M.N. ; writing--original draft preparation, M.N., G.P. and L.P.; writing--review and editing, M.N. ; visualization, M.N., L.P. and G.A. ; supervision, L.P., G.P. and G.K.; project administration, L.P.; funding acquisition, L.P., G.P. and G.K. All authors have read and agreed to the published version of the manuscript.