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However long the investigation takes, it will start with an examination of the last 45 min. of Columbia's life. Commander Rick Husband fired his deorbit engines at 8:15 a.m. E.T. when the ship was high over the Indian Ocean. Half an hour--and half a world--later, it hit the edges of the atmosphere just north of Hawaii at an altitude of about 400,000 ft. (122,000 m). Shortly after, a faint pink glow began to surround the ship, as atmospheric friction caused temperatures to rise to between 750[degrees]F and 3,000[degrees]F across various parts of the spacecraft's exposed underbelly.
The astronauts, busy monitoring their deceleration, temperature, hydraulics and more, didn't have much time to watch the light show play out, and by the time the glow brightened from faint pink to bright pink to plasma white, the ship had arced around the planet into thick air and daylight. "It all happens so smoothly ... you hardly notice it," says retired astronaut Henry Hartsfield Jr., who piloted Columbia in the early 1980s.
On the ground, things were smooth too. At Cape Canaveral the conditions were perfect for landing, with temperatures in the low 70s and a light breeze blowing, well within NASA's wind limits. The families of some of the seven crew members had already been shown to the runway, assembling for their close-up view of the touchdown. The pit crew that takes custody of the shuttle and shepherds it back into its hangar was standing by to claim Columbia as soon as the crowd cleared. In Mission Control in Houston things were similarly routine. "Many of us came in today marveling at the fact that one of the most difficult things we deal with is weather and we didn't have any weather issues anywhere in the world," says chief flight director Milt Heflin.
The weather would soon seem irrelevant. At 8:53 a.m., when the ship was crossing over San Francisco, a data point flickered on monitors at Mission Control indicating that the flow of information recording the temperature of the hydraulic systems in Columbia's left wing had suddenly ceased. At 8:56, when the ship was somewhere over Utah, the temperature in the landing gear and brake lining--again on the left side--registered high. Two minutes later, three temperature sensors embedded in the skin on the left flank of the ship quit transmitting. A minute later, temperature sensors in the left tires winked out too. All these data hiccups were reported by the mission controllers to the flight director. Finally, when the spacecraft was about 207,000 ft. (63,000 m) above Texas, Charlie Hobaugh, the spacecraft communicator, alerted the crew.
"Columbia, Houston," he said. "We see your tire-pressure message."
"Roger," Husband responded. "Uh ..." All at once, communications were cut off as if by a knife, and with them went every other scrap of data coming down from the ship.
"Columbia, Houston," Hobaugh said. "Com check."
Static crackled back. "Columbia, Houston. UHF com check," Hobaugh said, as Mission Control switched channels.
Still no response.
"Columbia, Houston," Hobaugh repeated several more times, but still there was nothing. Mission controllers--at least the veterans--did not expect there would be.
"We lost all vehicle data," says Heflin. "That's when we began to know that we had a bad day."