The Flex End-to-End Simulator: From Concept Phase (A/B1) to Ground Segment and Operations (C/D)

ESA's FLEX/Sentinel-3 tandem mission aims at mapping Sun-induced fluorescence (SIF) as a proxy to quantify photosynthetic activity of terrestrial vegetation. Due to the complexity of the mission concept and stringent requirements for the data processing algorithms, ESA developed a Phase A/B1 End-to-End Mission Performance Simulator (E2ES) tool to reproduce the expected mission performance and check the mission and instrument concepts. In the current Phase C/D, the E2ES concept must evolve to consolidate the whole data processing chain, providing an accurate figures of the whole mission error budget and serving as a roadmap for the future development of FLEX Ground Segment. This paper gives an overview of the activities involving the FLEX E2ES, from the conceptual development phase (Phase A/B1) to the implementation of the Ground Segment and operations (Phase C/D). Particularly, we will focus on the high-level description of the Level-2 data processing chain from an architecture and software design point of view.