In what promises to be an emotional day for the shuttle-station teams in orbit and on the ground, Collins and her crewmates will bid farewell to Krikalev and Phillips during a departure ceremony shortly before Discovery undocks from the lab complex on the 11th day of the mission.

Flight Day 11 highlights:

   DAY..EDT........DD...HH...MM...EVENT
      
   05/24/05
   Tue  04:11 AM...09...12...00...STS crew wakeup
   Tue  04:41 AM...09...12...30...ISS crew wakeup
   Tue  06:26 AM...09...14...15...Farewell ceremony
   Tue  06:41 AM...09...14...30...Egress and hatch closure
   Tue  08:41 AM...09...16...30...Undocking timeline begins
   Tue  09:26 AM...09...17...15...UNDOCKING
   Tue  11:56 AM...09...19...45...STS off-duty time begins
   Tue  08:11 PM...10...04...00...STS crew sleep begins

Flight Day 12 highlights:

   DAY..EDT........DD...HH...MM...EVENT
      
   05/25/05
   Wed  04:11 AM...10...12...00...Crew wakeup
   Wed  06:41 AM...10...14...30...Flight control system checkout
   Wed  06:41 AM...10...14...30...Cabin stowage begins
   Wed  07:51 AM...10...15...40...RCS hot-fire tests
   Wed  08:36 AM...10...16...25...Collins and Kelly rehearse landing procedures
   Wed  11:36 AM...10...19...25...Deorbit review
   Wed  04:11 PM...11...00...00...KU-band antenna stow
   Wed  07:11 PM...11...03...00...Crew sleep begins

"We're not changing anything as far as our trajectory planning or designing," Cain said. "We know we're right down the middle where we want to be. Of course, we've looked at all of that again. (But) we're going to continue to fly the way we've flown and what we consider to be the most benign entry profile we can do."

The shuttle's re-entry trajectory will carry the ship over the south Pacific Ocean, Central America, the Gulf of Mexico and then across Florida. The WB-57 jets will be in place west and east of the region of peak heating to document the shuttle's return. Engineers are hopeful the infrared sensors carried by the jets will help characterize the super-hot plasma around the spacecraft and perhaps improve understanding of at least some of the phenomena seen in amateur video of Columbia's descent.

But video from the modified WB-57 bombers will not be available until the day after landing.

In the wake of the Columbia mishap, NASA conducted studies to determine what risk a returning shuttle posed to the public in the event of another Columbia-class breakup at high altitude. Columbia's debris "footprint" was enormous, stretching almost all the way across Texas and into Louisiana. No one was injured by falling debris, but there were numerous close calls.

Based on population centers and the shuttle's ground track when returning from the space station, agency planners concluded the safest landing site, from a public risk perspective, was the Kennedy Space Center in Florida.

"We're going to plan to land at KSC, that's our prime landing site," Cain said. "Of course, our first line of defense and our prime rationale for flying to begin with is fixing the tank and the orbiter mods and the inspection and repair capability. We think that that rationale bolsters our ability to get back to KSC from a public risk standpoint.

If the weather or some other issue prevents a Florida landing, NASA will fall back on Edwards Air Force Base, Calif., and a backup site - Northrup Strip - at White Sands, N.M.

"The only difference is that if you look at the expectation of casualty information, there are some areas for Edwards and one specific area for Northrup where the public risk assessment is a little bit higher than the highest KSC entry approach. In other words, what was said fundamentally is any and all approaches into KSC are at a risk level that's equitable and acceptable from an agency policy standpoint. If you look at all the opportunities for all cross ranges to KSC and you look at all the areas that you're overflying during the entry ... it's all acceptable.

"When you go and plot that out for Edwards and Northrup, there are some areas that poke up above that line that defines the highest risk into KSC," Cain said. "You're going to have some cases where you're flying over the LA basin. And then even for Northrup, you've got a couple of cases where you fly over Mexico City or even the LA basin.

"So what we've said is, if I can't get into KSC for weather or whatever and I'm going to land at Edwards or Northrup, we're going to give consideration to not utilizing those approaches that have those higher public risk estimates that poke out above that line."

Flight Day 13 highlights:

   DAY..EDT........DD...HH...MM...EVENT
      
   05/26/05
   Thu  03:11 AM...11...11...00...Crew wakeup
   Thu  05:06 AM...11...12...55...Group B computer powerup
   Thu  05:21 AM...11...13...10...Inertial measurement unit alignment
   Thu  06:04 AM...11...13...53...Deorbit timeline begins
   Thu  10:04 AM...11...17...53...Deorbit ignition
   Thu  11:07 AM...11...18...56...Landing

"We've made a lot of progress in the last several months," Hale said. "We've been doing major work in a lot of different areas for return to flight. ... We are beginning, I think, to really converge on how to operate as a team and make effective decisions so that we can ensure we have a safe space flight."

Even so, Hale stressed that NASA will not catch "go fever" and launch Discovery before it's safe to fly.

"We are going to fly when we have determined that the vehicle is ready to fly, when it is safe to fly," he said. "We're not being driven by a calendar date, we're being driven by our readiness to go fly. So when we are convinced the external tank is in a good situation, when we are convinced we have the warning devices, the OBSS and all those other things, wing leading edge sensors all installed, checked out and ready to go, when we are convinced we have an adequate repair capability, then we'll go fly."

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