Exploring Cosmic Origins with CORE: Survey requirements and mission
  design
  Future observations of cosmic microwave background (CMB) polarisation have
the potential to answer some of the most fundamental questions of modern
physics and cosmology. In this paper, we list the requirements for a future CMB
polarisation survey addressing these scientific objectives, and discuss the
design drivers of the CORE space mission proposed to ESA in answer to the "M5"
call for a medium-sized mission. The rationale and options, and the
methodologies used to assess the mission's performance, are of interest to
other future CMB mission design studies. CORE is designed as a near-ultimate
CMB polarisation mission which, for optimal complementarity with ground-based
observations, will perform the observations that are known to be essential to
CMB polarisation scienceand cannot be obtained by any other means than a
dedicated space mission.
