The Apollo 1 fire during a countdown test on Jan. 27, 1967, left three astronauts dead. The Challenger explosion during liftoff on Jan. 28, 1986, left seven dead. The Columbia breakup during re-entry on Feb. 1, 2003, killed seven more.

Seventeen casualties all because of lousy human judgment.

"It's a time to continually, continually remind ourselves of what the price is for getting this wrong," O'Keefe said earlier this month. "There are seven families that will live with this forever, and it's something we can't any single day ever forget."

NASA's redemption for Columbia is moving forward, slowly, in small, sometimes barely perceptible ways.

These days the e-mailed gripes to the boss from NASA employees are often signed. More workers stand up at meetings and ask questions. More time is spent in making careful decisions.

Not everyone on the inside likes what they see in terms of cultural shift, including the widower of one of the Columbia astronauts. Some of the accident investigators who assailed NASA for its broken safety culture still hear grumbling from the lower working levels, and say they're not surprised.

But those at the top appear to be working hard to eradicate fear of reprisal for speaking out, one of the flaws in the system that doomed Columbia.

"Obviously, that kind of attitude comes from the top down," says Jose Garcia, a retired space shuttle operations manager who took his complaints about NASA safety cutbacks all the way to the White House in 1995.

Garcia keeps in touch with many of his former co-workers and the word is, "things are getting better, they're headed in the right direction."

The fact that NASA is putting aside its "bunker mentality" and seeking outside help to achieve cultural change is encouraging, says Diane Vaughan, a Boston College sociologist who assisted in the Columbia inquiry.

"They are up against the obstacle of time, of course, because it takes a long time to change culture," says Vaughan, author of the 1996 book, "The Challenger Launch Decision." "But I think that the step to bring in outsiders to consult with is a very important one."

Flags will fly at half-staff at NASA centers Thursday through Monday, when a memorial to the Columbia crew will be dedicated at Arlington National Cemetery, right next to the Challenger crew memorial.

NASA employees are being asked to also remember the two men who died in a helicopter crash in Texas last March while searching for Columbia wreckage.

Dr. Jon Clark, a NASA neurologist who lost his wife Laurel aboard Columbia, is among those dissatisfied with the state of cultural affairs one year later. He says he sees and hears enough to know that resistance persists.

"The people who don't sit there and see themselves in the report and see ways they can improve things, they're the ones who need to go," Clark says. "In other words, they embrace change, but it's changing somebody else, not them."

Clark says one of his colleagues, a psychiatrist, volunteered to work at the new NASA Engineering and Safety Center in Virginia, an outgrowth of the Columbia disaster. He was told, "No, no, we only want engineers."

"That's the exact kind of attitude, that it's not an engineering problem, per se," that needs to change, Clark says. "You need sociologists and psychologists, you need the soft sciences because they're the ones who are going to tell you when people start having intuitive feelings, you better start listening."

Garcia worries time will take its toll, just as it did after the Challenger accident, and that budget crunches and schedule pressures will start piling up once more.

"The fact that we're changing back now doesn't really shock me based on past history. That's really what we've done every time" following an accident," he says. "Now will we sustain it? That's the key here, whether we sustain it or not."