At a Thursday morning pre-launch briefing, Shuttle Weather Officer Kathy Winters said there is only a 30% change of favorable weather for a Friday morning launch.

When the shuttle does lift off, it will be the start of a 13-day mission that will have its four-person crew delivering supplies, a major experiment and spare parts to the . NASA has been trying to load up the station with supplies and spare parts to sustain its operations once the shuttle fleet is no longer flying missions.

The experiment loaded on Atlantis is washing machine-size mockup of what basically is a gas station in space.

The Robotic Refueling Mission is an experiment that will be attached to the outside of the space station where astronauts will use the station's to test the tools that would be needed to robotically refuel satellites.

Atlantis, which was rolled out on March 6, 1985, has flown 32 flights and 111.3 million miles.