NASA announced that the rotating service structure has been rolled away from space shuttle Endeavour in a major milestone leading up to launch. The liftoff of Endeavour on the STS-123 mission remains on schedule for 2:28 a.m. EDT Tuesday, March 11, NASA officials said.

The movement of the enclosed gantry clears the way for the loading of about 500,000 gallons of supercold liquid oxygen and liquid hydrogen propellants into the orange external tank this evening.

The rotating service structure provides weather protection to the shuttles at the launch pad and gives technicians access to the shuttle.

Endeavour's crew includes Commander Dominic Gorie, Pilot Gregory Johnson and Mission Specialists Rick Linnehan, Robert Behnken, Mike Foreman and the Japan Aerospace Exploration Agency's, Takao Doi. Endeavour is launching with the expectation of staying in space for 16 days, and there are always extra days set aside in case weather or a technical problem delays landing.

NASA has scheduled five spacewalks for the mission STS-123. During the first three spacewalks, the astronauts will install the first pressurized section, Japanese Experiment Logistics Module (ELM-PS), of the future Kibo (Hope) Japanese module and the Canadian Space Agency’s newest contribution to the station, the Special Purpose Dexterous Manipulator or Dextre.

“If you had to go to a drawing board and describe an exciting mission from scratch, I think you’d come up with STS-123,” Dominic L. Gorie, the flight commander said during a news conference.

The current weather forecast calls for only a 10 percent chance atmospheric conditions will delay the launch, with the primary concern coming from a slight chance of a low cloud ceiling around Kennedy.

Fueling of the external tank begins at 5:03 p.m.  and it should be complete by 8 p.m.. Endeavour's crew is expected to begin strapping in for launch just after 11 p.m. Monday. Endeavour is expected to return to Kennedy Space Center, March 26 at 8:35 p.m. ET.