A magnitude 9.0 earthquake, the strongest ever recorded in Japan and the fourth largest on world record since 1900, occurred in the Pacific Ocean near the Tohoku region at 14:46 JST (GMT+9) on 11 March 2011. The earthquake and subsequent tsunami caused massive destruction along the Tohoku-Kanto Pacific coast. The catastrophe was named the Great East Japan Earthquake and also refers to the accident at the Fukushima Daiichi Nuclear Power Plant. This paper presents actions taken by the Japan Aerospace Exploration Agency (JAXA), in collaboration with domestic and overseas institutions that assessed local post-earthquake conditions using earth observation satellites. This paper draws on lessons learnt from emergency operations during the disaster by examining JAXA's activities.