 STS-125 was first assigned to Discovery with a launch date no earlier than May 2008. This originally moved the mission ahead of STS-119, ISS Assembly flight 15. Delays to several shuttle missions resulted in a change in mission ordering, and the orbiter was changed to Atlantis on 8 January 2007. The crew of Atlantis went to the Kennedy Space Center for the Crew Equipment Interface Test in early July 2008. This allowed the STS-125 crew to get familiar with the orbiter and the hardware they would be using during the flight.
