Two spacewalkers will go to work outside the International Space Station today to replace a broken gyroscope. The huge gyroscope is used to keep the orbiting outpost in its proper position. It will take more than six hours for astronaut Rick Mastracchio and his Canadian colleague Dave Williams to remove the broken hardware and install the new component. Meanwhile, NASA experts continue to analyze the problems with damaged thermal tiles on the shuttle and could decide as early as today if the astronauts need to repair them or Endeavour is safe to land "as is."
