The mission was approved in November 2009, after years in proposal and planning as part of the European Space Agency's Horizon 2000+ programme; it is the last mission of the programme to be launched.
Misia bola schválená v novembri 2009, po rokoch návrhov a plánovania v rámci programu Európskej vesmírnej agentúry Horizont 2000 +.