For aid workers in South Asia, one of the most invaluable tools available are satellite images of the areas hit by the tsunami catastrophe. The bird's eye views from space help them determine which areas have been most deeply affected by the disaster and where they might still be able to rescue survivors. Four years ago, the European Space Agency (ESA) and the French space authority (CNES) established the International Charter of "Space and Major Disasters," a program that provides aid organizations and governments around the world with access to satellite data and images during catastrophes.

Click on the photo to access the gallery of satellite images.

Day and night, governments of countries that are members of the International Charter can request data from the organization. Since the Dec. 26 tsunami, the United Nations, the French Civil Protection Authority and the Indian space agency have all ordered images. In addition to the European members of ESA, Argentina, Canada, India, Japan and the United States are all Charter members.