Briefly explain the purpose of the International Space Station, and list the name of all space agencies involved in building and operating it. When is the assembly of the station expected to be completed? Include the name and the expected date of launch of the last module to be added.

Briefly explain the purpose of the International Space Station, and list the name of all space agencies involved in building and operating it. When is the assembly of the station expected to be completed? Include the name and the expected date of launch of the last module to be added.