The internal NASA investigation that found no evidence to support allegations of astronauts showing up drunk for missions appeared to close the book on the matter – but that was before congressional testimony by the head of the external panel that brought it to light in the first place.

U.S. Air Force Col. Richard Bachmann, testifying Sept. 6 before the House Science space and aeronautics subcommittee, raised the very plausible possibility that NASA investigators either did not talk to the right people or were unable due to the ground rules involved to elicit corroborating statements. In other words, Col. Bachmann, whose panel was chartered in February to investigate astronaut health issues, is sticking to his story – NASA’s own findings notwithstanding.

In a different way, Col. Bachmann’s surprising

testimony contrasted with his performance during a July 27 press conference in which he

reluctantly divulged specifics about the allegations in his report, which by then had already touched off a media-feeding frenzy that made NASA and its astronaut corps the object of public ridicule.

To be sure, there is nothing funny about astronauts showing up drunk for the most important day of their professional lives; such behavior would put not only lives but also hundreds of millions of dollars of taxpayer investment at risk. It is egregious – and likely criminal – misconduct that cannot be tolerated under any circumstances. But Col. Bachmann said during the press conference that his panel did not find it necessary to verify the allegations. “The committee was not concerned in the details of the specific incidents to the degree where we felt compelled to get names and dates and times,” he said. “It was not a legal investigation. We did not take sworn testimony or depositions or make transcripts.”

Whether or not the panel exercised good judgment in not running these allegations to ground – and nonetheless including them in the report – is debatable. But the lack of verification surely made it all that much easier to accept the notion that the alleged incidents never occurred, especially after NASA’s own investigation, led by Bryan O’Connor, the agency’s chief of safety and mission assurance, came up empty.

In his congressional testimony, Col. Bachmann provided additional details about his investigation and how it differed from NASA’s. He said the drunken astronaut allegations were based on information provided by eyewitnesses. He noted that to ensure the greatest candor possible from those interviewed, the panel members made every effort to keep names, places and dates out of their notes. The interviews conducted by Mr. O’Connor’s office, by contrast, were on the record.

This of course does not prove that the allegations are true any more than NASA can prove they are not: As NASA Administrator Mike Griffin correctly pointed out both before and during the hearing, it is impossible to prove a negative. But just as it was difficult to entertain the possibility that astronauts – admired for their courage, skill and professionalism – would behave so irresponsibly, it is difficult now to buy into Mr. Griffin’s Aug. 29 suggestion that the incidents were the stuff of urban legend.

There’s no mystery in the fact that interviews conducted with guarantees of anonymity produced a different result than those destined for the public record. This is a well-known, common-sense investigative principle: It is why key witnesses in criminal proceedings often are granted immunity from prosecution – or, for that matter, why many sources for news stories go unnamed.

Astronauts certainly have been known to have a drink or two; but it probably is fair to say that their alcohol consumption habits have moderated over the years, as have those of the general population. Whether NASA needs a new rule barring excessive drinking by astronauts in the year before they are scheduled to launch, as Mr. O’Connor has proposed, is questionable – simply defining “excessive” is problematic since alcohol tolerance levels vary widely.

The question of whether NASA astronauts were impaired on launch day in the recent past – and if so, which ones – remains open. However, the value of repeating Mr. O’Connor’s investigation, only this time with guarantees of anonymity for those interviewed, is dubious: It is highly unlikely that people already on the record as saying one thing or another would be willing to change their stories.

The larger issue, raised directly in Col. Bachmann’s report and subsequent testimony, is that NASA still has a ways to go in terms of instilling a culture where personnel feel free to speak up on flight safety issues without fear of reprisal and with confidence that their concerns will be heard. The importance of the latter should not be underestimated.

The report said that in the two incidents where astronauts were alleged to have arrived drunk at the launch pad, on-site managers permitted them to fly even after being alerted to the situation.

A lack of effective communication channels between NASA’s rank-and-file safety engineers and those responsible for launch decisions was cited in the wake of the February 2003, Space Shuttle Columbia accident. The concerns identified by the astronaut health panel are eerily similar. As part of its response to the panel’s findings, NASA is conducting an anonymous survey to identify weaknesses in this area. Lawmakers should carefully scrutinize the resulting report, and view with suspicion any conclusion that everything is A-OK.