The Columbia Accident Investigation Board is making "significant progress" analyzing video, still photographs, radar data and other sources of civilian and government data to more precisely determine where debris shed early in the shuttle Columbia's re-entry might have fallen, the board reported today.

Late this evening, NASA's mishap response team, which reports to the CAIB, issued a news release saying investigators are searching the Caliente, Nev., area for debris believed to have been tracked by air traffic control radar during Columbia's descent.

"Video imagery of Columbia's entry provided to NASA was analyzed by imagery, trajectory and ballistics experts," the release said. "The results of that analysis were then provided to National Transportation Safety Board officials who reviewed air traffic control radar imagery in that area during the time of Columbia's descent.

"The review resulted in what is believed to be a significant radar track of a piece of debris as it fell to Earth. As a result, a search of the Caliente area near the Nevada-Utah border is under way using Civil Air Patrol assets. A search using additional means also may be forthcoming."

The statement said about 25,000 pounds of shuttle debris has been transported to the Kennedy Space Center, about 11 percent of Columbia's re-entry weight.

Meanwhile, a group of experts making up the the Advanced Sightings Team is coordinating and analyzing data from NASA, the public, the Department of Defense, the Department of Energy, the National Oceanic and Atmospheric Administration, the United States Geologic Survey and "all other sources of valuable information that become available."

A press release said collaboration by all federal agencies "has been outstanding" and "the team is piecing together the information from these sources to learn as much as possible about anomalous conditions during the entry of Columbia."

The release said information under analysis includes:

• On-orbit photography and analysis by the DOD (presumably entry footage shot at a military installation in Hawaii)
• Military radar searches
• Sonic boom analysis
• Military radar coverage of the possible separation of debris while Columbia was in orbit
• Military analysis of launch footage
• Military identification of debris shedding events
• Analysis of a photograph taken at Kirtland Air Force Base, N.M.

To get a sense of the wide range of assets available to the board, consider the sonic boom analysis. An infrasound array in Lajitas, Texas - about 500 miles south of Dallas - recorded the sound of multiple detonations as Columbia broke up.

"The signal was recorded at about 14:30 GMT," according to a Southern Methodist University web site. "It shows a gradual ramp up of signal followed by a series of sharp events that appear to be explosions, somewhere between 7 and 12 separate events, with one widely spaced small event near the end. It took the sound wave about 30 minutes to arrive at the infrasound array in Lajitas, Texas."

Another SMU Department of Geology web page shows a fascinating animation of radar data from the National Weather Service showing the path of falling debris across Texas.

Shuttle engineers attempting to reconstruct the accident are especially interested in any debris that might have fallen away earlier in Columbia's descent to pinpoint exactly where the failure began. Telemetry indicates hot plasma worked its way into Columbia's left wing and ultimately triggered a catastrophic structural failure. But it's not yet known where the burn through occurred. Recovery of any debris shed early in the descent likely would shed light on the origin of the failure.

Gene Blevins, a freelance photographer who works with the Los Angeles Daily News, was photographing Columbia's re-entry from a radio telescope facility in California. He was among the first to see the sort of debris shedding that interests the Accident Board.

"Once we got our cameras set up, sure enough, around 5:52, 5:53 (a.m. Pacific Time), sure enough, here comes this big white dot out over the mountains coming right at us," Blevins said in a telephone interview. "Once it got a little more north of us, this thing was coming in at incredible speed. That's why I set my cameras up in advance."

After triggering his cameras, "I was looking straight north and I could see little red, like lava chunks, falling off from it ... flaking off from it and then getting sucked back into the plasma trail," Blevins said.

Blevins' 1-megabyte photograph, especially when magnified with image processing software, clearly shows two flaring events in the plasma trail toward the left of the image.

He didn't immediately think anything of it. But as the shuttle moved away and his cameras stopped shooting, "I saw this big red flare come from underneath the shuttle and being forced downward. I was like, 'whoa!'" He turned to another photographer, Bill Hartenstein, and said "Bill, did you see that? Something came off the shuttle!"

The Advanced Sightings Team of the Columbia Accident Investigation Board "is analyzing video footage turned in by space flight enthusiasts and other sources of information to document exactly when these events occurred," today's board statement said. "The earliest shedding of shuttle hardware may well have been documented by videos taken near the California coast. The team identifies anomalous events from the video data and correlates them to the entry timeline.

"Analysts calculate the exact time and angles of the observation by determining exactly where the videos were taken from and by identifying planets or star fields in the background. The team calculates trajectories to predict probabilities of where the debris may have fallen to Earth by estimating properties of possible debris from the video and incorporating known atmospheric and wind data. Radar data is then retrieved and investigated to search for specific signatures. This process serves to drastically reduce the area that must be searched.

"The Advanced Sightings Team is making significant progress in accurately characterizing possible debris events. They are in the process of making the subsequent calculations and taking the next steps. The most western find is still not far from Fort Worth, Texas. Using this process and other possible means, we hope debris discovered farther west would help to unravel the mystery of why this tragedy occurred."