ATHENA - System design and implementation for a next generation x-ray telescope

ATHENA, Europe's next generation x-ray telescope, has recently been selected for the 'L2' slot in ESA's Cosmic Vision Programme, with a mandate to address the ' Hot and Energetic Universe' Cosmic Vision science theme. The mission is currently in the Assessment/Definition Phase (A/B1), with a view to formal adoption after a successful System Requirements Review in 2019. This paper will describe the reference mission architecture and spacecraft design produced during Phase 0 by the ESA Concurrent Design Facility (CDF), in response to the technical requirements and programmatic boundary conditions. The main technical requirements and their mapping to resulting design choices will be presented, at both mission and spacecraft level. An overview of the spacecraft design down to subsystem level will then be presented (including the telescope and instruments), remarking on the critically-enabling technologies where appropriate. Finally, a programmatic overview will be given of the on-going Assessment Phase, and a snapshot of the prospects for securing the 'as-proposed' mission within the cost envelope will be given.