ASPERA-3 (Analyzer of Space Plasma and Energetic Atoms) is one of seven scientific instruments aboard the orbiting Mars Express spacecraft, performing remote sensing measurements designed to answer questions about the Martian atmosphere, structure, and geology. ASPERA-3 measures ions, electrons and energetic neutral atoms in the outer atmosphere to reveal the number of oxygen and hydrogen atoms (the constituents of water) interacting with the solar wind and the regions where such interaction occurs.

The ASPERA-3 instrument has four sensors to gather the data, along with a data processing unit and a scanning platform. Two of the sensors, the Electron Spectrometer (ELS) and the Ion Mass Analyzer (IMA) Imaging Detector, were funded by NASA as a Discovery Mission of Opportunity.