Science Requirement Document (SRD) for the European Solar Telescope (EST) (2nd edition, December 2019)

The European Solar Telescope (EST) is a research infrastructure for solarphysics. It is planned to be an on-axis solar telescope with an aperture of 4 mand equipped with an innovative suite of spectro-polarimetric and imagingpost-focus instrumentation. The EST project was initiated and is driven byEAST, the European Association for Solar Telescopes. EAST was founded in 2006as an association of 14 European countries. Today, as of December 2019, EASTconsists of 26 European research institutes from 18 European countries. The Preliminary Design Phase of EST was accomplished between 2008 and 2011.During this phase, in 2010, the first version of the EST Science RequirementDocument (SRD) was published. After EST became a project on the ESFRI roadmap2016, the preparatory phase started. The goal of the preparatory phase is toaccomplish a final design for the telescope and the legal governance structureof EST. A major milestone on this path is to revisit and update the ScienceRequirement Document (SRD). The EST Science Advisory Group (SAG) has been constituted by EAST and theBoard of the PRE-EST EU project in November 2017 and has been charged with thetask of providing with a final statement on the science requirements for EST.Based on the conceptual design, the SRD update takes into account recenttechnical and scientific developments, to ensure that EST provides significantadvancement beyond the current state-of-the-art. The present update of the EST SRD has been developed and discussed during aseries of EST SAG meetings. The SRD develops the top-level science objectivesof EST into individual science cases. Identifying critical science requirementsis one of its main goals. Those requirements will define the capabilities ofEST and the post-focus instrument suite. The technical requirements for thefinal design of EST will be derived from the SRD.