CAPE CANAVERAL, Fla. -- Just before it disintegrated, space shuttle Columbia experienced an abnormal rise in temperature and wind resistance that forced the craft's automatic pilot to make rapid changes to its flight path -- possible evidence that some heat-protection tiles were missing or damaged, NASA said Sunday.
Engineers began assembling a grim puzzle from debris recovered in Texas and Louisiana, and disclosed computerized data showing that the unusual events before Saturday's accident occurred in the wheel well and fuselage on the left side of the shuttle -- the same side hit by a piece of fuel-tank insulation during the launch 16 days earlier.
Shuttle program manager Ron Dittemore cautioned the data was preliminary but said the combination of events and data suggest that the thermal tiles that protect the shuttle from burning up during re-entry may have been damaged on Jan. 16.
"We've got some more detective work. But we're making progress inch by inch," Dittemore said, adding engineers are trying to extract 32 seconds more of computerized data from the doomed spacecraft.
As engineers pinpointed the exact satellite locations of debris, Robert Cabana, director of flight crew operations at the Johnson Space Center, said remains from all seven of the astronauts had been found. Later, Cabana said in a statement that he had been misinformed and that NASA could not confirm that remains from each of the astronauts were recovered.
Dittemore said earlier in the mission, NASA had aggressively investigated the possible effects of the impact from the fuel tank's foam insulation and concluded "it did not represent a safety concern."
"As we gather more evidence, certainly the evidence may take us in another direction," he said.
Dittemore said the engineering data showed a rise of 20 to 30 degrees in the left wheel well about seven minutes before communication was lost with the spacecraft. Then there was a rise of about 60 degrees over five minutes in the lefthand side of the fuselage above the wing, he said.
On the right side, the shuttle temperature rose the normal 15 degrees over the same period, he said. All the readings came from sensors underneath the thermal tiles, on the aluminum hull of the craft.
The temperature rises were followed by increased drag on the spacecraft that caused its automated flight system to adjust its path, he said. The adjustments were large enough that "we have never seen it to this degree," but still were within the shuttle's capabilities, he said.
Communication with the shuttle was lost soon after. "It was if someone had cut the wire," Dittemore said.
The left side of the spacecraft has been the focus of suspicion almost from the start. Investigators are focusing on whether a broken-off piece of foam insulation from the big external fuel tank caused damage to the shuttle's left wing during liftoff Jan. 16 that ultimately doomed the flight 16 days later.
The manufacturer of the fuel tank disclosed Sunday that NASA used an older version of the tank, which the space agency began phasing out in 2000. NASA's preflight press information stated the shuttle was using one of the newer super-lightweight fuel tanks.
Harry Wadsworth, a spokesman for Lockheed, the tank maker, said most shuttle launches use the "super-lightweight" tank and the older version is no longer made. Wadsworth said he did not know if there was a difference in how insulation was installed on the two types of tanks.
Wadsworth said the tank used aboard the Columbia mission was manufactured in November 2000 and delivered to NASA the next month. Only one more of the older tanks is left, he said.
Dittemore said the tank, though no longer manufactured, had been used for many years and was between 6,000 and 7,000 pounds heavier than the newer version, but "we had no reason to doubt it capability."
Earlier Sunday, NASA administrator Sean O'Keefe named a former Navy admiral to oversee an independent review of the accident, and said investigators initially would focus on whether the piece of insulation caused the damage that brought down the shuttle.
"It's one of the areas we're looking at first, early, to make sure that the investigative team is concentrating on that theory," O'Keefe said.
The insulation is believed to have struck a section of the shuttle's left side.
O'Keefe emphasized that the space agency was being careful not to lock onto any one theory too soon. He vowed to "leave absolutely no stone unturned."
For a second day, searchers scoured forests and rural areas over 500 square miles of East Texas and western Louisiana for bits of metal, ceramic tile, computer chips and insulation from the shattered spacecraft.
State and federal officials, treating the investigation like a multi-county crime scene, were protecting the debris until it can be catalogued, carefully collected and then trucked to Barksdale Air Force Base in Louisiana.
The effort to reconstruct what is left of Columbia into a rough outline of the shuttle will be tedious and painstaking.
When a shuttle piece was located this weekend, searchers left it in place until a precise global position satellite reading could be taken. Each shuttle part is numbered; NASA officials say experts hope to trace the falling path of each recovered piece.
The goal is to establish a sequence of how parts were ripped off Columbia as it endured the intense heat and pressure of the high-speed re-entry into the atmosphere.
At least 20 engineers from United Space Alliance, a key NASA contractor for the shuttle program, were dispatched to Barksdale for what is expected to be a round-the-clock investigation.
Other experts, including metallurgists and forensic medicine specialists, are expected to join the investigation. Their focus will be on a microscopic examination of debris and remains that could elicit clues such as how hot the metal became, how it twisted and which parts flew off first.
In addition to NASA's investigation, O'Keefe named an independent panel to be headed by retired Navy admiral Harold W. Gehman Jr., who previously helped investigate the 2000 terrorist attack on the USS Cole.
Gehman's panel will also examine the Columbia wreckage, and come to its own conclusions about what happened. O'Keefe described Gehman as "well-versed in understanding exactly how to look about the forensics in these cases and coming up with the causal effects of what could occur."
Joining Gehman on the commission are four other military officers and two federal aviation safety officials.
Officials used horses and four-wheel-drive vehicles to find and recover the shuttle pieces. Divers were being called in to search the floor of Toledo Bend Reservoir, on the Texas-Louisiana line, for a car-sized piece seen slamming into the water.
Recovered body parts may be sent to a military morgue at Dover Air Force Base in Delaware.
Columbia came apart 200,000 feet over Texas while it was streaking at more than 12,000 miles an hour toward the Kennedy Space Center. A long vapor trail across the sky marked the rain of debris.