CAPE CANAVERAL, Fla. -- Here is a timeline of events, as released by NASA, that begins with the de-orbit burn and ends with the last understanding of telemetry received from Columbia. This information is expected to change from day to day as some facts are added, others adjusted.
Last updated as of 7 a.m. EST (1200 GMT) Tuesday, Feb. 4:
8:15:18 a.m. EST (1315.18 GMT) -- Columbia's twin orbital maneuvering engines, each capable of generating 6,000 pounds of thrust, were fired for two minutes and 38 seconds, slowing the shuttle by 176 mph. At the time it was over the Indian Ocean roughly 5,000 miles away from the Kennedy Space Center. Columbia's orbital path required only about 14 miles of crossrange flight toward the right.
8:43:53 a.m. EST (1343.53 GMT) -- Columbia reaches entry interface, the official point about 75 miles high that NASA defines as the place where the vehicle first begins to encounter traces of Earth's atmosphere. It's at this time the vehicle begins to slow from orbital velocity of 17,500 mph and the crew begins to feel the first tugs of gravity. Outside the first hints of re-entry heat start.
8:49:26 a.m. EST (1349.26 GMT) -- Because Columbia is a glider and has only one shot at landing, the shuttle enters the atmosphere with excess altitude and speed, or with too much "energy." To dissipate that energy so the shuttle doesn't overshoot the runway, the shuttle flies a couple of sweeping S-turns. The first of these starts now, with Columbia rolling onto its right wing at an angle of 23 degrees.At this same time the shuttle's nose is up about 40 degrees, the crew have long since been strapped into their seats and the onboard computers are flying the re-entry profile with the help of inputs from sensors and other guidance and navigation equipment located all over the spaceplane.
8:51 a.m. EST (1351 GMT) -- Columbia crosses the California coast north of San Francisco and is seen on the ground.
8:52 a.m. EST (1352 GMT) -- The first indication that something is going wrong is recorded when three left main landing gear brake line temperature sensors detect a rise. The shuttle is flying over California.
8:53 a.m. EST (1353 GMT) -- Two more sensors in the left-hand wheel well (left brake line strut actuator and uplock actuator temperature sensors) detect an increase in temperature of 30 to 40 degrees Fahrenheit in five minutes. At the same time, four sensors near the elevon at the back of the wing failed off, suggesting their wiring was severed somewhere.
8:54 a.m. EST (1354 GMT) -- Sensors on the outside wall of Columbia's fuselage above the left wing shows a 60-degree rise in temperature in five minutes, while the sensors on the right side showed a more normal 15-degree rise -- an indication that a significant heating problem was taking place on the left side. Temperatures inside the cargo bay are normal. The shuttle was over eastern California and western Nevada.
8:55 a.m. EST (1355 GMT) -- Another main gear brake line temperature sensor shows an unusual temperature rise.
8:57 a.m. EST (1357 GMT) -- Two sensors on the left wing's upper and lower skin failed off. The shuttle is flying over Arizona and New Mexico.
8:58 a.m. EST (1358 GMT) -- The elevon flaps on the left wing began moving to steer the shuttle on course after computers detected the shuttle was beginning to fly off course due to increased drag on the left wing. At the same time, wheel well sensors measuring temperature and pressure of the left main-landing gear failed. The shuttle is over New Mexico.
8:59 a.m. EST (1359 GMT) -- Two of Columbia's nose steering jets automatically fired for 1.5 seconds to help the shuttle counteract the rapidly increasing drag on the left wing. The shuttle is over west Texas.
8:59:22 a.m. EST (1359.22 GMT) -- Loss of signal happened at 15 days, 22 hours, 20 minutes and 22 seconds after launch. Columbia was 207,000 feet high and moving 18 times the speed of sound, or more than 12,000 mph.
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