NASA is leading the Artemis missions, but it has several international partners, both from the public and private sectors. More than a dozen countries have signed the Artemis Accords, which lay out shared principles grounded in safety and transparency for governing space exploration, as well as scientific and commercial activities in space. Some of NASA's biggest collaborators are sure to send their own crew members on Artemis missions. Earlier this year, the US committed to including a Japanese astronaut aboard the lunar Gateway outpost. The US also expressed its support for sending a future Japanese astronaut to the moon as part of the Artemis program.The European Space Agency is also a significant contributor to the Artemis program. The ESA, for instance, designed Orion's service module -- the part of the spacecraft that supplies air, electricity and propulsion. In exchange for the service modules, the ESA will receive three seats on future Artemis missions, Space News reported.