APEX is a Swiss-Belgian project for the realization of an airborne imaging spectrometer within the framework of the ESA Prodex Programme. The project’s emphasis is on delivering products characterized by high level accuracy to the user community. This objective relies on the concept and the actuation of two fundamental phases: (a) instrument calibration and (b) data processing. An accurate instrument calibration procedure is required in order to achieve a proper knowledge of the instrument behavior. The calibration information is structured into calibration cubes. These calibration cubes are then integrated into the specialized processing for data calibration to convert the raw system data into physical (spectral, radiometric, spatial) units. Higher-level products can be ordered and configured by the end users via according web interfaces. The dedicated APEX Processing and Archiving Facility (PAF) is hosted and operated by VITO.