Measuring Ultra-High-Energy Cosmic Rays from Earth Orbit: From the TUS Project to K-EUSO and Beyond

The K-EUSO project developed in the JEM-EUSO collaboration for installation on board the International Space Station is described. A number of technological projects are successfully executed during its preparation: the EUSO-Balloon and EUSO-SPB1 balloon experiments, and the telescope as part of the Telescope Array (EUSO-TA). Since 2019, a wide-angle detector “UV atmosphere” (Mini-EUSO) has been operating on board the ISS Russian Segment. After K-EUSO, it is planned to conduct the even more ambitious POEMMA (Probe of Extreme Multi-Messenger Astrophysics) experiment to register both ultra-high energy cosmic rays (UHECR) and high-energy neutrinos.