Ariel was selected in 2018 as the fourth medium-class science mission in ESA’s Cosmic Vision plan. It was ‘adopted’ by ESA during the Agency’s Science Programme Committee meeting on 12 November.
ESA’s exoplanet mission Ariel, scheduled for launch in 2029, has moved from study to implementation phase, following which an industrial contractor will be selected to build the spacecraft.
Press release:

Exoplanet mission timeline. Credit: ESA