ISO 20214:2015 is intended as a high-level systems engineering reference to enable engineers to better understand the layered security concepts required to secure a space system. As such, this document is a Security Architecture for Space Data Systems (SASDS). This architecture uses the views described in the Reference Architecture for Space Data Systems (reference [B1]) developed by the CCSDS Architecture Working Group. The SASDS will be used: ? to establish an overall CCSDS conceptual framework for the incorporation of security into the data systems of space missions; ? to define common language and representation so that risks, requirements, and solutions in the area of security within space data systems can be readily communicated; ? to provide a source of information for the security architects on a space mission to use to develop the system security design; ? to facilitate development of standards in a consistent way so that any standard can be used with other appropriate standards in a system.