The scientific objectives of DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) are the detection and characterization of the ionospheric perturbations associated with natural phenomena (such as earthquakes, volcanic eruptions, tsunamis) or with anthropogenic activities. To achieve these objectives, the microsatellite, which was launched at the end of June 2004, surveys the Earth's electromagnetic environment. DEMETER is the first in the Myriade series of microsatellites developed by the Centre National d'Etudes Spatiales (CNES, France) for low-cost science missions.