EChO was proposed as an M-class candidate mission for the Cosmic Vision 2015-2025 programme in response to the Call for Proposals issued by ESA in October 2010. In February 2011 it was selected for further assessment and study.

The initial definition of the science and mission requirements for EChO has been completed, along with a preliminary reference design for the payload. An ESA-internal study was conducted in the Concurrent Design Facility (CDF) at the European Space Research and Technology Centre (ESTEC) with the goal of performing a first iteration on a spacecraft design for EChO that fulfills all mission requirements. The goal was met, with a feasible proof-of-concept mission realized within the CDF study. This concept will be studied further by ESA. The results of the CDF study will be used to prepare an open Invitation to Tender to be issued to industry in Autumn 2011. The industrial activities will have a typical duration of about 1 year.

In parallel, studies of the EChO instrument will be carried out by consortia of scientific institutes selected by ESA through an open call and financially supported by the ESA Member States.