entry has always been a critical moment of space travel. The shuttle has to slow from its orbit speed of about 28,000 kilometres per hour to a speed that allows safe re-entry. To achieve this, the shuttle flies backwards and upside-down and fires its orbital manoeuvring engines in what is called the re-entry burn. The shuttle is not turned around until just before it hits the atmosphere and is then positioned so that the heat shield at its bottom will take the brunt of the strain. It takes about an hour to slow down the spacecraft enough to allow it to land. Because there is no more fuel on board after the re-entry burn, the shuttle glides toward its landing strip. Discovery's landing approach will be much steeper and faster than those of commercial planes and it will lower its landing gear just seconds before touching down. Once the shuttle hits the ground, a parachute is released to break its speed. According to NASA's most recent timetable, Discovery is scheduled to land in Florida at 0837 GMT Monday morning. Because of a series of technical problems with Discovery, NASA weighed up the risks involved in the return flight precisely before giving the shuttle the go-ahead. In an unprecedented repair in space, astronaut Steve Robinson removed gap filler from the shuttle's heat shield by hand Wednesday. Mission control informed the crew Thursday that, after making repairs to the underside of the shuttle during a spacewalk, they would not have to repair a puff in an insulation blanket outside Discovery. --mor 1142 Local Time 0842 GMT
