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CAPE CANAVERAL -- The morning fog was burning off at Kennedy Space Center as Mission Control gave the seven astronauts aboard Columbia the go-ahead to come home.
"I guess you've been wondering, but you are 'go' for the de-orbit burn," Mission Control radioed Saturday morning.
Columbia fired its thrusters at 8:15 a.m., preparing for re-entry. All appeared normal and the plan was to land about an hour later in Florida.
For 38 minutes, there was no clue that anything was wrong. Communications between the ground and the shuttle routinely are lost during the fiery re-entry through Earth's atmosphere.
Columbia, the oldest shuttle in NASA's fleet, was traveling at more than 16,400 mph as it approached the California coast.
Typically the spacecraft commander, Rick Husband, and pilot, William McCool, would sit in the control seat at the front windshield. Just behind, at McCool's right shoulder, would be Laurel Blair Salton Clark, a physician. And behind both the pilot and commander was astronaut Kalpana Chawla. In a tight compartment below the cockpit, were the other three astronauts, Michael Anderson, David Brown, and Ilan Ramon, the first Israeli astronaut.
At 8:53 a.m., NASA lost temperature measurements for the shuttle's left hydraulic system.
Five minutes later, NASA lost measurements from three temperature sensors on Columbia's left side.
Around the same time, astronomers at the California Institute of Technology say, Columbia was trailing fiery debris as it passed over eastern California, sending out bright flashes and pieces, as if dropping flares.
At 8:59 a.m., eight more temperature measures and pressure measures for the left inboard and outboard tires disappeared. One measurement remained visible to the crew on a display panel; which the crew acknowledged.
Mission Control radioed back: "Columbia, Houston, we see your tire pressure messages and we did not copy your last."
Husband, the shuttle commander, calmly responded: "Roger, uh, buh . . ."
For several seconds, silence.
The temperature at that point of re-entry: 3,000 degrees. The altitude: 207,135 feet, or 39 miles above Earth.
Again and again and again and again Mission Control called, first on one radio channel and then on another. But the silence stretched on.
Their voices remained calm despite growing evidence that Columbia and its astronauts were in great trouble.
About the same time, residents of north Texas heard a loud explosion. Video cameras recorded multiple contrails spraying outward from the spacecraft.
"I was getting ready to take my dogs for a walk . . . sitting in my family room and looking out the window and suddenly saw a streak absolutely screaming across the sky," said Ron Wasilewski, 57, of Frisco, Texas.
"It was a huge ball of fire with pieces breaking off of it," Wasilewski said. "I thought it was a meteor going to pieces."
Wasilewski said he walked outdoors and ran into a neighbor who saw the streak.
"Initially, you saw a contrail in the sky, like a jet plane or something, but on closer observation you could see at the end of the contrail was a huge fireball," said Wasilewski, who works in sales and marketing for dental laboratory in Garland, Texas.
About two minutes later, he said, there were a series of explosions.
"There were about five explosions," he said. "They were so big you could feel it like vibrations in the air.
The debris rained over hundreds of miles of fields and highways, stretching from near Dallas all the way into Louisiana.
At Cape Canaveral, the countdown clock reached zero at 9:16 a.m. with an eerie silence and no sign of the shuttle.
NASA declared an emergency at 9:29 a.m.
Inside Mission Control, flight controllers pulled out emergency procedures. NASA also ordered them to retain all their records.
The controllers hovered in front of their computers, staring at the screens. The wives, husbands and children of the astronauts who had been waiting at the landing strip were gathered together and taken to a separate place.
Soon after 9:30, search and rescue teams were being mobilized in the Dallas and Fort Worth areas.
Across the nation, the news began to spread. Cell phones rang at soccer games. A hushed buzz spread from cashier to customer at grocery stores.
On television, cartoons gave way to images of the Columbia disintegrating as it plunged to the ground. Another reminder of vulnerability. Another unnerving disaster with the nation still healing from the Sept. 11 terrorist attacks.
"With all that is happening these days, it's a very bad feeling," said Nancy Mitchell, a hardware store clerk in Confluence, Pa. "It's just one more thing -- a tragedy."
The Federal Aviation Administration issued a notice to airmen because the National Weather Service radar picked up a debris cloud about 95 miles long and 13 to 22 miles wide over Lake Charles, La.
At 9:44 a.m., NASA asked members of the public to help in its search for debris, but warned people not to touch the pieces because they might be contaminated with toxic rocket fuel.
At 11 a.m., Kennedy Space Center lowered its flag to half staff, but NASA didn't immediately declare the crew dead. That job would be left to the president.
President Bush rushed back from Camp David in the Maryland mountains by motorcade, instead of helicopter because of the drizzly weather, and arrived at the White House about 12:15 p.m.
At 2:05, President Bush addressed the nation: "Columbia is lost; there are no survivors."
-- This report was compiled by Ron Brackett using information from Times wires and Pat Farnan.