before a rescue flight is launched. FD-45→47 The rescue flight catches up with the ISS, conducting heat shield inspections en route. FD-47 The rescue flight docks with the station, on day three of its mission. FD-48 Shuttle crew enters the rescue orbiter. Vehicle with a crew complement of 11 undocks from ISS. FD-49 Rescue orbiter re-enters atmosphere over Indian or Pacific Ocean for landing at either Kennedy Space Center or Edwards Air Force Base. A Russian Progress resupply spacecraft is launched at later date to resupply ISS crew. ISS precautionary de-crew preparations begin. FD-58 De-crew ISS due to ECLSS O2 exhaustion in event Progress unable to perform resupply function. STS-125 rescue plan STS-400 was the Space Shuttle contingency support (Launch On Need) flight that would have been launched using if a major problem occurred on during STS-125, the final Hubble Space Telescope servicing mission (HST SM-4). Due to the much lower orbital inclination of the HST compared to the ISS, the shuttle crew would have been unable to use the International Space Station as a "safe haven", and NASA would not have been able to follow the usual plan of recovering the crew with another shuttle at a later date. Instead, NASA developed a plan to conduct a shuttle-to-shuttle rescue mission, similar to proposed rescue missions for pre-ISS flights. The rescue mission would have been launched only three days after call-up and as early as seven days after the launch of STS-125, since the crew of Atlantis would only have about three weeks of consumables after launch. The mission was first rolled out in September 2008 to Launch Complex 39B two weeks after the STS-125 shuttle was rolled out to Launch Complex 39A, creating a rare scenario in which two shuttles were on launch pads at the same time. In October 2008, however, STS-125 was delayed and rolled back to the VAB. Initially, STS-125 was retargeted for no earlier than February 2009. This changed the STS-400 vehicle from Endeavour to Discovery. The mission was redesignated STS-401 due to the swap from Endeavour to Discovery. STS-125 was then delayed further, allowing Discovery mission STS-119 to fly beforehand. This resulted in the rescue mission reverting to Endeavour, and the STS-400 designation being reinstated. In January, 2009, it was announced that NASA was evaluating conducting both launches from Complex 39A in order to avoid further delays to Ares I-X, which, at the time,