"The mission marks the first time in seven years a space shuttle is going somewhere other than the International Space Station. Atlantis and its crew are going to the Hubble Space Telescope, which is in a completely different orbit than the space station, and that makes a world of difference. The Hubble’s orbit is considerably higher and “dirtier” than the ISS. Hubble is about 350 miles above the earth, while the space station is just over 200 miles. The extra altitude will expose Atlantis to more pieces of space junk, any of which could potentially slam into the shuttle. The odds of a catastrophic strike by orbital debris is something NASA has been closley monitoring, and there it an estimated one-in-221 chance of a debris collision with shuttle Atlantis.
“We’re not performing the RPM, the pitch maneuver for this flight, so we have to come up with some substitutes for that,” said Tony Ceccacci, the mission’s lead flight director. “On Flight Day 1, we’ll be doing an upper crew cabin survey. It’s about a 45-minute task, and we’ll have to do this in the daylight.” Flight Day 2 consists of more damage surveys. In all, it will take over 9.5 hours to make sure the shuttle is free from damage. If there is damage, the crew would be stranded in their spacecraft at the Hubble, where NASA estimates they could stay alive for 25 days before losing oxygen. That’s where shuttle Endeavour comes into play. Endeavour and four more astronauts would need to blast off on a rescue flight as soon as NASA determines Atlantis is too damaged to fly home.

