FACTBOX-Discovery launches on 120th shuttle mission

Space shuttle Discovery blasts off from its launch pad at the Kennedy Space Center in Cape Canaveral, Florida October 23, 2007. Discovery is on a mission to the International Space Station.

(Reuters) - The 26-year-old U.S. space shuttle program has launched 120 flights -- including Discovery's mission on Tuesday -- and has 13 to go before the fleet is retired.

Discovery's launch sets the stage for the arrival of partner laboratories to the International Space Station.

Here are some facts about the mission.

* Space shuttle Discovery is on its 34th flight and the third of four shuttle missions planned for this year.

* The shuttle's fuel tank originally was to fly on the first mission after the 2003 Columbia disaster. It served as a test article before it was rebuilt and recertified for flight.

* The Harmony module aboard the shuttle is the first new addition to the space station's living space since September 2001.

* The Harmony module was built in Italy by the European Space Agency, which took on the cost of building it in exchange for NASA launching its lab and other components to orbit.

* Harmony joins three U.S. station segments -- the Destiny lab, Unity node and Quest airlock.

* The spacecraft with which NASA intends to replace the shuttle, called Orion vehicles, are being designed to dock at Harmony.

* During Discovery's 10-day stay at the station, five different astronauts will make spacewalks.