Endeavour set for space mission on Monday

Space shuttle Endeavour Commander Mark Kelly and his crew returned to the Kennedy Space Centre to prepare for a second launch attempt to the International Space Station.Endeavours first launch attempt on April 29 was called off about four hours before liftoff when engineers detected a problem with a heating system in one of the ships onboard power units. Technicians replaced an electronics switching box and rewired the circuit.NASA is retiring its three-ship shuttle fleet this summer due to high operating costs and to develop spaceships that can travel beyond the stations orbit.