WASHINGTON, Feb 1: US Space Shuttle Columbia disintegrated Saturday on its return to Earth, a process which takes about an hour from leaving orbit to touchdown.

During a normal re-entry, a space shuttle first enters the atmosphere at an altitude of about 130kms, some 8,000kms from its landing strip.

It enters the atmosphere at a 40 degree angle to the horizon with its wings level.

At this position the shuttle’s heat shield protects it from temperatures of up to 1,650 degrees C.

NASA lost contact with Columbia in the middle of the re-entry process, when it was flying at an altitude of 63kms, at a speed of 20,000 kilometres per hour.

BUSH: US President George Bush vowed on Saturday that space exploration would continue despite the loss of the space shuttle and the deaths of its seven-person crew.—AFP