Welcome to ASPERA-3, the first Mission of Opportunity to be selected as part of the Discovery Program. The ASPERA (Analyzer of Space Plasmas and Energetic Atoms) experiment is one of seven scientific instruments that will fly on the European Space Agency’s (ESA) Mars Express mission, planned to launch in mid-2003. The main objective of the mission is to search for sub-surface water from orbit and drop a lander on the Martian surface. The instruments onboard the orbiting spacecraft will perform remote sensing measurements designed to answer questions about the Martian atmosphere, the planet’s structure and geology. The Mars Express team consists of ESA engineers, industry and hundreds of international scientists.