CAPE CANAVERAL, Fla. - The shuttle Endeavour astronauts scanned their ship on Thursday for damage from micrometeoroid impacts in advance of departing the International Space Station on Sunday for a return to Earth.

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The routine inspection is typically done two days before landing, but the Endeavour crew will be leaving behind its sensor-laded inspection boom for use on the station.

It will be one of the last items delivered to the station before NASA ends the shuttle program after a final supply run aboard sister ship Atlantis in July.

Endeavour delivered its prime science experiment -- the $2 billion Alpha Magnetic Spectrometer -- and a pallet of spare parts. The crew plans to make a fourth and final spacewalk on Friday to help get the station ready for operations after the shuttle program ends.

The ships are being retired due to high operating costs and to free up funds for NASA to work on new spacecraft that can travel beyond the station's 220-mile- (355-km) high orbit where the shuttles cannot go.

Endeavour is due back at the Kennedy Space Center in Florida on Tuesday.