NASA postpones Discovery landing     After orbiting the earth for nearly two weeks, astronauts aboard space shuttle Discovery were told to circle the planet for another day as bad weather inprefix = st1 /Floridaforced NASA to delay Monday's scheduled landing.    The astronauts had powered up their space-craft and were awaiting word from Mission Control to fire their breaking rockets and head for home when controllers announced early Monday that low clouds over Cape Canaveral would postpone the landing.    When cloud cover still threatened after the second of two landing opportunities, NASA officials rescheduled the landing for Tuesday, when they would consider two alternative landing sites in addition to Florida'sKennedySpaceCenter.   Before the weather _ , Discovery had been set to land before dawn. Its return to the earth would have concluded the first shuttle flight sinceColumbiadisintegrated while re-entering the earth's atmosphere 21/2 years ago. Discovery's 13-day flight to the international space station may be the last one for a long while. NASA grounded the shuttle fleet after a slab of insulating foam  broke off  Discovery's external fuel tank during liftoff---the very thing that doomed(...) Columbia and was supposed to have been corrected. Discovery was the first shuttle to visit the station since 2002.    As a result ofColumbia, Discovery's crew inspected their ship for damage on five different days and also tested repair techniques developed since the tragedy. The astronauts received word from Mission Control   _  .
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