After a month out of public view, NASA's space shuttle program manager will be back in the spotlight Thursday as a witness at the first public hearing held by the Columbia accident investigation board.

Ron Dittemore was the face and voice of NASA in the week following the shuttle's breakup over Texas, describing the tragic events and their aftermath at daily news conferences at Johnson Space Center. That role ended when the investigation board took over.

On Thursday, Dittemore will be back answering questions, this time from board members instead of reporters.

It is the first in an onslaught of public hearings planned by the board's chairman, Harold Gehman Jr., a retired Navy admiral who led the investigation into the 2000 bombing of the USS Cole. He said he will hold hearings twice a week, every two out of three weeks, for the foreseeable future.

Even Gehman's own staff is surprised at the frequency.

"He wants his process to be open to the public," explained the Federal Aviation Administration's Laura Brown, the board's spokeswoman.

Astronaut Scott Altman, the commander of Columbia's next-to-last mission who is taking part in the investigation on NASA's behalf, reacted with a "wow" to the heavy schedule.

He said he is all for making the hearings open to the public, especially in space towns like Houston, Cape Canaveral, Fla., and Huntsville, Ala. That is where most of the hearings will be held.

In those places, "folks are pretty aware of what's going on and you may get some input or help in the long run," Altman, a Navy commander, said in an interview Wednesday. The only risk, he said, is that inviting the public could make the board feel more rushed to come up with answers, which might turn out to be the wrong ones.

"You don't want to be distracted by giving a public pitch and by doing PowerPoint charts when you want to be finding out what went wrong," he said.

The board suspects Columbia's left wing was breached, possibly by foam, ice or other debris that broke off from the shuttle's big external fuel tank during liftoff Jan. 16, and the hot gases of re-entry seeped inside 16 days later. All seven astronauts were killed.

Thursday's hearing will be held in a 500-seat theater at the University of Houston at Clear Lake, just a few miles from Johnson Space Center.

During his last news conference on Feb. 7, Dittemore pledged "unwavering support" to the board. "If there's anything they need, we will provide it," he said.

Gehman refused to say whether Dittemore was among the top-level shuttle managers that he requested be removed from the Columbia investigation because of a conflict of interest. NASA chief Sean O'Keefe has publicly contradicted Dittemore's contention that even if the space agency had known about the severity of damage to the thermal tiles on Columbia's wing, there is nothing anyone could have done about it.

Besides Dittemore, who has headed the shuttle program since 1999, Gehman plans to call as witnesses Thursday the Johnson Space Center director, the former director of NASA's Ames Research Center, and a Boeing engineer who is an expert on the foam that insulates the external fuel tank.

Jefferson Davis Howell Jr., a retired Marine lieutenant general who flew combat in Vietnam, has directed Johnson for the past year. He will open up the testimony so he can leave early to attend funeral services at Arlington National Cemetery in Virginia for three of the Columbia crew.

Henry McDonald, a Scottish-born engineer who teaches at the University of Tennessee at Chattanooga, served as director of Ames in Mountain View, Calif., from 1996 through 2002. He headed a shuttle assessment team that concluded in 2000 that budget and staffing cuts had forced NASA to turn over too much of its safety oversight to outside contractors -- and that safety was being superseded by schedule and cost-cutting.

The board also will hear from tank foam expert Keith Chong, an engineer who works for Boeing in Huntington Beach, Calif.

"We're going to get a little bit of the theory of foam before we start going into who did what to whom and whether it was done correctly," Gehman said.

To increase its scientific heft, the board added three new members Wednesday, bringing the total number to 13: the first American woman in space, Sally Ride, a physicist; a Nobel-prize winning physicist, Douglas Osheroff of Stanford University; and director of the Space Policy Institute at George Washington University, John Logsdon. None of the new members will attend Thursday's hearing.