A constellation of 36 CubeSats built by Universities Teams from 23 countries around the world to perform first-class science in the largely unexplored lower thermosphere at 200–380 km altitude. The project receives funding from the European Union’s Seventh Framework Programme for Research and Technological Development. The satellites, which have been progressively deployed since June 2014 from both the International Space Station (ISS; NanoRacks-QB50 project) and Earth, formed a complete constellation in June 2017. The mission’s principal goal is to achieve a sustained and affordable access to space for small-scale research space missions and planetary exploration.