Douglas Osheroff, a Nobel Prize winner and member of the Columbia Accident Investigation Board fears more tragedies will follow.

"It's easy to be receptive six months after a major accident. The question is whether it's going to last," he says.

According to investigators, Columbia was struck by the same failures in judgment and communication that caused the loss of the shuttle Challenger in 1986 - after which NASA vowed reforms to make sure its checks and balances would never fail again.

But they did. Long-standing trouble with fuel tank foam insulation that struck Columbia was deemed a maintenance problem, not a significant safety issue. Concerns about the issue were not flagged up the chain of command.

NASA will follow recommendations by the independent board investigating the Columbia accident to the letter and will make no effort to defend itself against findings that are expected to be harsh when released later this month, according to a top space official.

"There will be no effort whatsoever to argue or defend," Frederick Gregory, NASA's deputy administrator, told reporters at the Kennedy Space Center. "We will respond to each of the findings and recommendations. In fact, I would expect we would go farther than that."

Members of the board headed by retired Adm. Harold Gehman have been sharply critical of the culture in which life-and-death decisions have been made at NASA. The investigation has probed deeply into the program's history, sometimes characterizing it as a series of compromises dating back to the 1960s.

Reporters repeatedly asked Gregory about potential changes in the culture that decides whether a shuttle is safe to fly and whether its crew can survive the mission, but Gregory, a former astronaut himself, said it would be difficult to respond until the report had actually been delivered.

Once the Gehman board has issued its report, a 27-member task force, headed by retired astronauts Tom Stafford and Richard Covey, will begin overseeing NASA's efforts to implement the new recommendations.

"We will not fly until we are ready, until we have some assurance from the task group that we are headed down the right road," said Gregory.

Some watchdogs wonder about the "true depth of the agency's soul searching," as described in a Florida Today editorial.

"To alter NASA's culture will first require agency managers to admit there is a problem - something they have yet to do - and acknowledge they no longer are the sole keepers of the right stuff. Only then can real change occur," said the paper.