Katrin Schroeder ^1* Mireno Borghini ²

• ¹ Institute of Marine Science, Department of Earth System Sciences and Technologies for the Environment, National Research Council (CNR), Venezia, Italy
• ² La Spezia, Institute of Marine Science, Department of Earth System Sciences and Technologies for the Environment, National Research Council (CNR), Venezia, Veneto, Italy

Oceanographic mooring missions are critical for advancing our understanding of the world's oceans and their role in the broader Earth system. These missions rely on the deployment and maintenance of complex observing systems, comprising subsurface, profiling, and surface moorings, which are designed to collect valuable data from the ocean interior. The success of these missions depends on meticulous planning and strategic execution, which are facilitated by the use of Field Service Plans (FSPs). FSPs are comprehensive and adaptable planning tools that integrate safety measures, contingency plans, and timelines to ensure the successful and safe recovery, maintenance, and deployment of mooring systems. In this paper, we provide a comprehensive guide to drafting, implementing, and adapting FSPs tailored to the unique challenges posed by oceanographic mooring missions. We highlight the critical role of FSPs in optimizing safety, data quality, and mission success, while also underscoring the need for flexibility and adaptation. Our aim is to provide practical guidance and a template for researchers, expedition leaders, and institutions engaged in oceanographic research.Start date End date Key persons Pre-cruise planning phase: In this phase, detailed planning activities take place, including the definition of objectives, selection of deployment sites, mooring design, checking of equipment list and mooring diagram, instrument calibration, request of necessary permits and authorizations, shipping of equipment. T0 -T180 T0 -T30 FA, PI, TE, VC, DM, RB & EA Recovery Phase: At the end of a deployment period, the mooring is recovered from the deployment site. This phase involves vessel operations, winch or crane operations, careful handling of sensors and instruments, and data backup. T0 T1 TE, PI, RB & VC Post-recovery on-board operations phase: This phase includes routine maintenance, sensor checks, and monitoring of mooring functionality. Regular maintenance operations, including battery replacement, sensor calibration, and the replacement of sensors with recalibrated units, occur as needed.