STS-131 was an ISS assembly flight with the primary payload being a loaded Multi-Purpose Logistics Module - Leonardo. The mission began on April 5th 2010 at 1021:22 UTC launching Commander Alan Poindexter, Pilot James Dutton, Mission Specialist 1 Richard Mastracchio, Mission Specialist 2 Dorothy M. Metcalf-Lindenburger, Mission Specialist 3 Stephanie Wilson, Mission Specialist 4 Naoko Yamazaki & Mission Specialist 5 Clayton Anderson to orbit. They docked with the ISS 2 days after launch. The mission was the final Space Shuttle launch with a seven person crew and was the longest flight for Discovery. STS-131 also marked the first time 4 women have been in space at once. During the mission 3 spacewalks were conducted to replace an ammonia tank and to retrieve a seed experiment from outside the Japanese laboratory. The mission concluded after 15 days & 2 hours on April 20th 2010 at 1308:35 UTC after 2 waved off landing opportunities on the 19th at the Kennedy Space Center.
The International Space Station programme is tied together by a complex set of legal, political and financial agreements between the sixteen nations involved in the project, governing ownership of the various components, rights to crewing and utilization, and responsibilities for crew rotation and resupply of the International Space Station. It was conceived in 1984 by President Ronald Reagan, during the Space Station Freedom project as it was originally called.