HOUSTON -- In the moments before Columbia broke apart over Texas, an astronaut may have tried to override the shuttle's autopilot, according to officials familiar with an analysis of the final bits of data.
But one official close to the investigation stressed: "The data are really suspect. They can't ensure the integrity of any of the data, and some of the stuff that they're saying may be inaccurate or misinterpreted."
A NASA spokeswoman, Eileen Hawley, also said any attempted override could have been unintentional; in other words, one of the pilots may have bumped the control stick.
The new information was presented to the Columbia accident investigation board Sunday. ABC News reported the data showed one of the crew may have tried to take over the spaceship before its destruction during its Feb. 1 re-entry.
For weeks, in an attempt to reconstruct what went wrong, NASA and other experts have been analyzing data transmitted in the last 32 seconds of flight. The final two seconds of data, which follow 25 seconds of nothing, indicate there was an input to disengage the autopilot system, the official said.
The computer-operated autopilot never went off, the official noted, possibly because there was not enough time for it to do so - or perhaps because there was no attempt by the crew to override it.
"Had you had more data after two seconds, you might know whether it would have gone off or not," the official said. It is difficult if not impossible to know "whether that was unintentional or whether it was intentional or whether it even occurred at all," the official said.
Hawley pointed out that even before Columbia started re-entering the atmosphere, commander Rick Husband accidentally bumped the stick but quickly corrected for it. Under normal conditions, moving the stick turns off the autopilot.
Minutes later, "there is some evidence that the stick may have been bumped" again, Hawley said. But she added that part of the problem is that the data are intermittent, with a high error rate, "and to draw any conclusions from it would be really wrong."
The data also suggest the four steering jets that automatically began firing to try to compensate for increased drag on the left side of the spacecraft were no longer able to counteract the forces, the official said.
"It kind of indicates the orbiter was out of control, basically," the official said.
Investigators suspect a breach in the left wing allowed the searing gases of atmospheric re-entry to penetrate the shuttle and set off the cascade of catastrophic events.
The data suggest there were no readings coming from Columbia's left orbital maneuvering system in the final two seconds, which could mean it broke off or was badly damaged along with the left wing, said the official close to the investigation.
NASA is reconstructing, as best it can, the timeline of Columbia as it flew across the Pacific, crossed the California coast and continued its descent over Nevada and New Mexico and Texas, en route to a Florida touchdown following a 16-day science mission. All seven astronauts were killed.
The board, meanwhile, suspects that the hot gases probably entered the shuttle through a breach along the leading edge of the left wing. The blowtorch-like gases may have snaked their way through the wing and streamed out the left main landing gear compartment.
Earlier in the investigation, the board believed the gases may have entered this left wheel well, but is more inclined now to think the gases were actually coming out, the official said.
"It's a strong theory. It has a certain amount of support," the official said.
The board is still trying to determine whether launch debris caused the breach. Insulating foam or other debris broke off Columbia's external fuel tank barely a minute into the flight Jan. 16 and struck the left wing.
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