In line with the overall Sentinel operations strategy, Sentinel-1, the next European C-Band SAR mission following ERS and ENVISAT, will be operated based on a stable and predefined observation scenario. During the Full Operations Capacity of the mission, this observation scenario will make optimum use of the SAR duty cycle within the technical constraints of the overall system, with the main objective of satisfying the observation requirements from the GMES services and for use by ESA and EU Member States, as stipulated in the ESA GMES Space Component Programme Declaration. In addition, a secondary objective is to some extent ensure the continuity of ERS/ENVISAT SAR data exploitation. The process of collecting the Sentinel-1 observation needs (from GMES services, Member States, the scientific community, etc.) and deriving the baseline observation scenario is on-going at the time of writing this paper. The paper describes this process at high level. It provides an overview of the main types of services and applications to be supported by Sentinel-1 and their high level observation requirements, as well as the overall strategy which is followed to define the related observation scenario.