The Columbia Disaster: A Chronology
1:30 a.m. CST, February 1, 2003 – The Entry Flight Control Team began duty in the Mission Control Center.
7:00 – Mission Control Center Entry Flight Director LeRoy Cain polled the Mission Control room for a GO/NO-GO decision for the de-orbit burn.
All weather observations and forecasts were within guidelines set by the flight rules, and all systems were normal.
7:10 – The Capsule Communicator (CAPCOM) notified the crew that they were GO for de-orbit burn.
7:15:30 (EI-1719) – Husband and McCool executed the de-orbit burn using Columbia's two Orbital Maneuvering System engines.
The Orbiter was upside down and tail-first over the Indian Ocean at an altitude of 175 miles (282 km) when the burn was executed. The de-orbit maneuver was performed on the 255th orbit, and the 2-minute, 38-second burn slowed the Orbiter from 17,500 miles per hour (7.8 km/s) to begin her re-entry into the atmosphere. During the de-orbit burn, the crew felt about 10% of the effects of gravity. There were no problems during the burn, after which Husband maneuvered Columbia into a right-side-up, forward-facing position, with the Orbiter's nose pitched up.
7:44:09 (EI+000) – Entry Interface (EI), arbitrarily defined as the point at which the Orbiter enters the discernible atmosphere at 400,000 feet (120 km; 76 mi), occurred over the Pacific Ocean.
As Columbia descended from outer space into the atmosphere, the heat produced by air molecules colliding with the Orbiter typically caused wing leading-edge temperatures to rise steadily, reaching an estimated 2,500 °F (1,370 °C) during the next six minutes. (As former Space Shuttle Program Manager Wayne Hale stated in a press briefing, about 90% of this heating is the result of compression of the atmospheric gas caused by the orbiter's supersonic flight, rather than the result of friction.)
7:48:39 (EI+270) – A sensor on the left wing leading edge spar showed strains higher than those seen on previous Columbia re-entries.
This was recorded only on the Modular Auxiliary Data System, which is similar in concept to a flight data recorder, and was not telemetered to ground controllers or displayed to the crew.
7:49:32 (EI+323) – Columbia executed a planned roll to the right. Speed: Mach 24.5.
Columbia began a banking turn to manage lift and therefore limit the Orbiter's rate of descent and heating.
7:50:53 (EI+404) – Columbia entered a 10-minute period of peak heating, during which the thermal stresses were at their maximum. Speed: Mach 24.1; altitude: 243,000 feet (74 km; 46 mi).
7:52:00 (EI+471) – Columbia was approximately 300 miles (480 km) west of the California coastline.
The wing leading-edge temperatures usually reached 2,650 °F (1,450 °C) at this point.
7:53:26 (EI+557) – Columbia crossed the California coast west of Sacramento. Speed: Mach 23; altitude: 231,600 feet (70.6 km; 43.9 mi).
7:53:46 (EI+577) – Signs of debris being shed were sighted by people out to watch. Speed: Mach 22.8; altitude: 230,200 feet (70.2 km; 43.6 mi).
The superheated air surrounding the Orbiter suddenly brightened, causing a streak in the Orbiter's luminescent trail that was quite noticeable in the pre-dawn skies over the West Coast. Observers witnessed another four similar events during the following 23 seconds. Dialogue on some of the amateur footage indicates the observers were aware of the abnormality of what they were filming.
7:54:24 (EI+615) – The Maintenance, Mechanical, and Crew Systems (MMACS) officer informed the Flight Director that four hydraulic sensors in the left wing were indicating "off-scale low." In Mission Control, re-entry had been proceeding normally up to this point.
"Off-scale low" is a reading that falls below the minimum capability of the sensor, and it usually indicates that the sensor has failed (stopped functioning, due to internal or external factors), rather than that the quantity it measures is actually below the sensor's minimum response value.
The Entry Team continued to discuss the failed indicators.
7:54:25 (EI+616) – Columbia crossed from California into Nevada airspace. Speed: Mach 22.5; altitude: 227,400 feet (69.3 km; 43.1 mi).
Witnesses observed a bright flash at this point and 18 similar events in the next four minutes.
7:55:00 (EI+651) – Nearly 11 minutes after Columbia re-entered the atmosphere, wing leading-edge temperatures normally reached nearly 3,000 °F (1,650 °C).
7:55:32 (EI+683) – Columbia crossed from Nevada into Utah. Speed: Mach 21.8; altitude: 223,400 feet (68.1 km; 42.3 mi).
7:55:52 (EI+703) – Columbia crossed from Utah into Arizona.
7:56:30 (EI+741) – Columbia initiated a roll reversal, turning from right to left over Arizona.
7:56:45 (EI+756) – Columbia crossed from Arizona to New Mexico. Speed: Mach 20.9; altitude: 219,000 feet (67 km; 41 mi).
7:57:24 (EI+795) – Columbia crossed just north of Albuquerque.
7:58:00 (EI+831) – At this point, wing leading-edge temperatures typically decreased to 2,880 °F (1,580 °C).
7:58:20 (EI+851) – Columbia crossed from New Mexico into Texas. Speed: Mach 19.5; altitude: 209,800 feet (63.9 km; 39.7 mi).
At about this time, the Orbiter shed a Thermal Protection System tile, the most westerly piece of debris that has been recovered. Searchers found the tile in a field in Littlefield, Texas, just northwest of Lubbock.
7:59:15 (EI+906) – MMACS informed the Flight Director that pressure readings had been lost on both left main landing-gear tires. The Flight Director then told the Capsule Communicator (CAPCOM) to let the crew know that Mission Control saw the messages and was evaluating the indications, and added that the Flight Control Team did not understand the crew's last transmission.
7:59:32 (EI+923) – A broken response from the mission commander was recorded: "Roger, uh, bu – [cut off in mid-word] ..." It was the last communication from the crew and the last telemetry signal received in Mission Control.
7:59:37 (EI+928) – Hydraulic pressure, which is required to move the flight control surfaces, was lost at approximately GMT 13:59:37. At that time, the Master Alarm would have sounded for the loss of hydraulics, and the shuttle began to lose control, beginning to roll and yaw uncontrollably, and the crew would have become aware of the serious problem.
8:00:18 (EI+969) – Videos and eyewitness reports by observers on the ground in and near Dallas revealed that the Orbiter had disintegrated overhead, continuing to break up into more and smaller pieces, and leaving multiple contrails, as it continued eastward. In Mission Control, while the loss of signal was a cause for concern, there was no sign of any serious problem. Prior to orbiter breakup at GMT 14:00:18, the Columbia cabin pressure was nominal and the crew was capable of conscious actions. The crew module remained mostly intact through the breakup, though it had lost enough structural integrity that it lost pressure, and was completely depressurized no later than 9:00:53.
8:00:57 (EI+1008) - The still intact crew module was seen breaking into small subcomponents. It disappeared from view at 9:01:10. The crew, if not already dead before, were dead no later than this point.
8:05 – Residents of Northeast Texas, particularly near Tyler, reported a loud boom, a small concussion wave, smoke trails and debris in the clear skies above the counties east of Dallas.
8:12:39 (EI+1710) – After hearing of reports of the shuttle being seen to break apart, the NASA flight director declared a contingency (events leading to loss of the vehicle) and alerted search and rescue teams in the debris area. He made a call to the Ground Controller: "GC; flight, GC; flight. Lock the doors." Two minutes later Mission Control put contingency procedures into effect. Nobody was permitted to enter or leave the room, and flight controllers had to preserve all the mission data for later investigation.
Sources: Wikipedia.com, NASA.gov