EChO is an M-class mission candidate within the science program Cosmic Vision 2015-2025 of the European Space Agency. It aims at characterising the atmosphere of known transiting exoplanets, potentially from giant Hot Jupiters down to Super-Earths orbiting in the habitable zone of M-dwarf stars.

It was selected in February 2011 to enter an assessment phase (phase 0/A). Following the completion of the Concurrent Design Facility study conducted by ESA in June/July 2011, two parallel industrial studies were carried out throughout 2012, and were then extended till August 2013. Similarly, two parallel instrument studies were conducted till mid-2012, following which an Announcement of Opportunity was released and concluded in February 2013 by the selection of a single instrument consortium.

This paper describes the status of EChO upon completion of the system level and instrument studies. It includes a discussion on the evolution of the science and mission requirements, the description of the final preliminary design and performance parameters, as well as programmatic estimates in terms of technology readiness and schedule.

The next step for EChO will consist of passing the Preliminary Requirements Review, planned by the end of 2013, followed by the down-selection of a single M3 mission.