In a few days, the space shuttle Endeavour will rollout to her ocean side launch pad right next to where her sistership Atlantis currently sits, to prepare for a possible rescue flight following Atlantis launch into space.
In the event that Atlantis' thermal tiles on her outerskin are damaged during her STS-125 launch and Mission Control states that reentry would be too risky, Endeavour would be called up on rescue mission STS-400.
STS-400 would see Endeavour launch with a crew of four from launch pad 39-B and into the same orbital inclination as Atlantis - 28.45 degrees to the earth's equator. After only one day of manuvers to catch up with the weakened Atlantis, Endeavour would slowly pull up and park her payload bay over her weakened sistership.
NASA's Shuttle Program Managers stated that Endeavour's 50-foot robotic arm would then latch Atlantis robotic arm so that both ships are then connected to begin crew rescue via spacewalks. Program managers also state that only the STS-125 crew of seven would spacewalk over to Endeavour's outside airlock during the span of several days.
Atlantis' spacewalking astronauts of John Grunsfeld and Andrew Feustel will depart Atlantis to prepare a rope which will assist fellow astronaut Megan McArthur over to Endeavour. The following day more of the crew will translate over concluding with Atlantis' skipper Scott Altman.
A few months ago, the Johnson Space Center said that the STS-400 crew would be made up of the commander, pilot, and two mission specialists from a recent space station mission - last November's STS-126 mission. Chris Ferguson would command STS-400, with pilot Eric Boe and mission specialists Robert Kimbrough and Stephen Bowen rounding out the crew.
A few days following Atlantis' May 12th launch, the STS-125 crew will use the robotic arm to survey the orbiter's tiles and thermal blankets along her wing leading edges, nose section and aft section. If issues with damaged tiles are seen, then two spacewalkers will venture outside to see if the damage can be repaired using an in flight maintenance kit.
If Atlantis is cleared for reentry, then Endeavour will be moved from Pad 39-B southward to Pad 39-A to be prepared for her prime mission STS-127 to the international space station.
Inside NASA, everyone we spoke with states that if Atlantis is deemed a loss while on orbit, it could mean the end of shuttle flights now instead of Autumn 2010 - the time when the shuttle fleet are set to retire.