Cape Canaveral, Fla. Flight controllers and others at NASA struggled to push away thoughts of Columbia's tragic return as Discovery aimed for a landing before dawn today, the first for a shuttle since the 2003 disaster.
The Mission Control team in charge of guiding Discovery and its crew of seven safely back to Earth was focused on that sole objective and trying not to dwell on that awful morning when the Columbia shattered in the sky just 16 short minutes from home and seven astronauts were lost.
"We're looking forward, we're not looking back," flight director LeRoy Cain said Sunday with less than 24 hours to go before touchdown.
So were Discovery's seven astronauts, who woke up Sunday evening ready to return home.
"I have had a lot of thoughts about Columbia and I will have thoughts after the landing," said commander Eileen Collins. "We're all going to be very focused ... on the job at hand."
"It's time to come home," she added Sunday, "and keep working on getting the shuttle better and ready to fly in the future."
Good weather was forecast for what was to be a relatively uncommon, less-preferred landing in darkness, something unavoidable given Discovery's launch time on July 26. Of the previous 111 shuttle touchdowns, only 19 occurred at nighttime.
Discovery's 13-day flight to the international space station and back may be the last one for a long while. NASA grounded the shuttle fleet after a slab of insulating foam broke off Discovery's external fuel tank during liftoff - the very thing that doomed Columbia and was supposed to have been corrected.
Unlike Columbia, which was punched in the wing, Discovery was not hit by the big chunk of foam, but other smaller pieces struck. No severe damage was noted by the brand new wing sensors, laser-tipped inspection boom and extensive photography, giving NASA the confidence to clear the spacecraft for the fiery, inherently dangerous ride home.
A torn thermal blanket under a cockpit window, most likely ripped by launch debris, was judged good enough for re-entry and left alone.
Cain said the unprecedented load of data posed "somewhat of a challenge" in that it gave him more things to consider for the one-hour descent.
"But I would tell you, I think as most of us would tell you, that I'd rather have more data because it makes me better prepared," he said. "I don't think, honestly, that it can add to my anxiety or list of things that I'll worry about or not worry about. The buffers pretty much fall either way."
Never before have astronauts or flight controllers known so much about the condition of a returning shuttle.
"That's a fantastic step forward," astronaut Stephen Robinson said from orbit Sunday. "The next step is to be able to repair any damage we happen to have found. Our shuttle didn't require any repair, just a tiny little dental flossing of plucking a couple of gap fillers out."
Robinson did the flossing during a spacewalk last Wednesday, easily pulling away two strips of thermal tile filler dangling from Discovery's belly. NASA feared the hanging material might lead to a repeat of the Columbia catastrophe and ordered the first-ever orbital repair to a shuttle's heat shield.
Collins' co-pilot, James Kelly, said he did not have any concerns about re-entry and noted that all the prelanding flight control checks went well.
"I guess you almost have to thank the Columbia crew," Kelly said. "The sacrifices they made allowed us to get a lot smarter about it, get a lot of tools on board that we could use to look at the vehicle."
Like other NASA officials, Cain stressed that Discovery looked "entirely clean" for the plunge from space.
Nonetheless, he expected to have butterflies in his stomach, just as he's had every other time he's entered Mission Control to direct a shuttle launch or landing. If he didn't have butterflies, "I'd probably turn right around and go back outside and find somebody else to do the job."
Cain was in the same flight director's seat for Columbia's re-entry on Feb. 1, 2003.
"There are a lot of things to think about. There are a lot of things to worry about," he said. "That's what I get paid to do is to worry - and I do it a lot."