Some aspects of the CubeMAP mission (also known as ESP-MACCS) are presented: its science objectives, and the primary choices made to address them from small satellite platforms. The science case, addressing some key scientific questions related to global change, is elaborated in four objectives focused on upper troposphere and stratospheric composition and its change. The sounding methodology and the associated observation concept retained is a constellation of miniature limb solar occultation thermal infrared sounders, offering the advantages of limb solar occultation, whilst mitigating the inherent lack of coverage of this geometry. The mission focuses on tropical regions as the gateway to the upper troposphere, and the stratosphere. The miniaturized instrument payloads developed for the mission are briefly presented: the High resolution InfraRed Occultation Spectrometer (HIROS) and the Hyperspectral Solar Disk Imager (HSDI). Lastly, the nanosatellite 12U platform and its subsystem are described, completing the overview of the mission space segment.