ESA issues call for Earth Explorer proposals As part of ESAs Earth Observation Programme and its continuing endeavour to address critical Earth science issues, the Agency has released an opportunity for scientists to submit proposals for the eighth Earth Explorer mission. By focusing on science and research, the Earth Explorer series of missions is being flown to improve our understanding of how the Earth system works and how human activity affects natural Earth processes. Earth Explorer missions also test cutting-edge technology for Earth observation, as the recent GOCE gravity mission is clearly demonstrating.