STS-120 will be the twenty-third mission to the International Space Station and will deliver the U.S. Node 2 Harmony module expanding the space station's capability for future international laboratories.

Built in Italy for the United States, Harmony is a high-tech hallway and Tinkertoy-like hub. It is a 23- by 14-foot passageway that will connect the U.S. segment of the station to the European and Japanese modules, to be installed later this year and early next year, respectively.

Harmony will be the first new U.S. pressurized component to be added to the station since the Quest Airlock was attached to one of Unity's six berthing ports in 2001.

“In the early days of the “space race”, as we called it then, it was a competition between the great nations of the world. Today, we are in cooperation with many international partners, including many of our former rivals and other allied nations, in a great expedition to build and complete construction of the first permanent outpost in space.” Space Shuttle Program Manager Wayne Hale said.

Air Force Col. Pamela A. Melroy will command the STS-120 mission to take the Node 2 connecting module to the station. Melroy is the second woman to command a shuttle.

NASA's Kennedy Space Center will hold a media event at 10 a.m. EDT, Tuesday, Sept. 18, to highlight the next piece to be added to the International Space Station.

NASA officials said they expect to add a fifth spacewalk to test some a tile patch repair equipment that could be used to fix heat-shield damage that can happen to shuttles during launch.

The so-called T-RAD was due to only be tested next year, but the trial was moved up in light of tile damage discovered during last month's Endeavour shuttle mission to the ISS.

On August 8, one minute after Endeavour’s launch, the debris, which likely had some SLA or ice attached, ricocheted off a metal strut to carve a gouge on space shuttle’s heat shield.

After Endeavour’s astronauts conducted a video inspection it was revealed that the gouge, located near the ship's right wheel well, was 30.5 x 25.5 millimeters (1.2 x 1.0 inches) large (smaller than initially reported) and 28.5 millimeters (1.12 inches) deep.

Though, NASA mission managers in Houston decided not to repair the space shuttle Endeavour’s heat shield. NASA said the damage was not enough to risk a catastrophic failure of the shuttle's heat shield, like the one that destroyed the shuttle Columbia on re-entry in February 2002, but the process of underside repairs during a spacewalk would have entailed risks for the astronauts.

On August 21, after twelve days spend in space, the space shuttle Endeavour landed safely at the Kennedy Space Centre in Florida, a day earlier than planned because of the hurricane Dean.

Next week, the launch of space shuttle Discovery on mission STS-120 moves one step closer as technicians are scheduled to roll the shuttle the short distance from the Orbiter Processing Facility to the giant Vehicle Assembly Building. The main payload for the mission, the Italian-built U.S. Harmony module for the International Space Station, will be loaded inside Discovery at the launch pad.