Harmony, a big Italian-made aluminum tube weighing in at 14.3 tonnes, will connect the two labs to the outpost and give it its almost final shape.

NASA plans to bring in the Columbus on an Atlantis shuttle flight December 6 and the Kibo early in 2008.

Discovery's crew of seven includes five men and two women, one of whom is Commander Pam Melroy, 46. The crew, which also includes an Italian, Paulo Nespoli, with the European Space Agency, was due to deliver a 16-tonne, 20-meter(yard)-long beam called P6.

Once in place, P6 will make it possible to deploy a third dual-wing solar antenna of the four which are planned. That will get the station's electrical power generation gearing up.

Five spacewalks of a total 30.5 hours by teams of two astronauts are planned for the 14-day mission, including 10 tied to the ISS.

The launch of the Discovery, the third of a shuttle this year and the 23rd to the ISS, is scheduled for Tuesday, October 23 at 1538 GMT at Kennedy Space Center in Florida, with a 10-minute window for blastoff.

Countdown formally started at 1800 GMT Saturday.

On Saturday, Cape Canaveral weather forecaster Kathy Winters gave a 60-percent chance of good weather for liftoff. She said possible rain and clouds could interfere with the launch.

The seven astronauts arrived in Houston, Texas late Friday to ready for the mission.

"All of our systems are in good shape," said Charlie Blackwell-Thompson, NASA Test Director.

Program officials decided to make the Tuesday launch attempt despite recommendations of an engineers committee calling first for the replacement of three of 44 thermal protection shields on the orbiter's wings.

"The Flight Readiness Review board decided we were in an acceptable risk posture to go fly," shuttle program manager Wayne Hale told reporters on Tuesday.

The bottom of the wings endure temperatures of 1,600 degrees Celsius when the shuttle makes reentry to the Earth's atmosphere at more than 20 times the speed of sound.

NASA has closely watched the shuttles' thermal tiles since the 2003 Columbia catastrophe when a tile broke off the shuttle as it took off and hit its wing. The damage caused the shuttle to break up on re-entry, killing all seven crew members.

Replacing the tiles would have taken two months time said Hale, a time frame that would have affected coming launches.

NASA plans at least an additional 11 flights to complete the ISS by 2010, when the shuttle fleet is supposed to be taken out of service.

The ISS is a 100 billion dollar project in which 16 countries are taking part to ready the way for future manned Mars missions.

earlier related report
STS-120 shuttle mission facts
The space shuttle Discovery and its crew of seven, including two woman an its Italian astronaut, will blast off Tuesday on a 14-day mission to attach a new module on the orbiting International Space Station.

- Shuttle: Discovery, one of NASA's three-strong shuttle fleet that includes the Endeavour and Atlantis.

- Launch: Tuesday, October 23, 11:38 am (1538 GMT), includes a 10-minute launch window. Blasts off from Kennedy Space Center, Cape Canaveral, Florida.

- Emergency landing sites after launch: Saragoza, Moron (Spain), Istres (France). If the shuttle is close enough, it could also return to Florida.

- Mission duration: 13 days, 18 hours, 9 minutes.

- Landing: earliest November 6 at 4:47 am (0947 GMT) at Kennedy Space Center, weather permitting. Alternative landing sites: Edwards Air Force Base, in California, or White Sands, New Mexico.

- Orbiting altitude: 225.3 kilometers (140 miles)

- Altitude when docking with ISS: 347.2 kilometers (216 miles)

- Mission overview: deliver and install cylindrical, pressurized Harmony module. Made of aluminum, the module will provide attachment points on the ISS for future European and Japanese modules. Harmony weighs 14.3 tonnes and measures 7.17 meters (25.5 feet) long by 4.42 meters (14.5 feet) in diameter.

- Spacewalks: five have been scheduled, ranging in duration from four to seven hours. They will take place on the 4th, 6th, 8th, 10th and 11th day of the mission.

- Shuttle weight on launch, including external fuel tank and twin engines: 2,053 tonnes.

- Shuttle weight on landing: 91.6 tonnes.

- Commander: Pamela Melroy, 46.

- Pilot: George Zamka, 45.

- Mission specialists: Scott Parazynski, 46, Stephanie Wilson, 41, Doug Wheelock, 47, Paulo Nespoli, 50, Italian with the European Space Agency, and Daniel Tani, 46, who will replace Clayton Anderson, 48, after a six-month stint on the ISS.

earlier related report
Shuttle Discovery crew
The crew of the US space shuttle Discovery consists of seven members, including two women and an Italian national representing the Europena Space Agency:

-- Pamela Melroy, 46, shuttle commander. Melroy retired from the Air Force in February 2007 with the rank of colonel. During her service, she logged more than 5,000 hours flight time in over 45 different aircraft. Melroy began her training to become astronaut at NASA's Johnson Space Center, in Texas in March 1995. She served as pilot on two shuttle flights, aboard the Discovery in 2000 and aboard the Atlantis in 2002, and has logged over 562 hours in space.

-- George Zamka, 45, pilot. A 1984 graduate of the United States Naval Academy, he served as a Marine Corps aviator in Japan, South Korea, Singapore, and in Southwest Asia. Zamka flew 66 combat missions over occupied Kuwait and Iraq during Operation Desert Storm. He has over 4000 flight hours in more than 30 different aircraft. Zamka began his astronaut candidate training in August 1998 and has served in various technical and leadership roles in the astronaut office.

-- Scott Parazynski, 46, mission specialist. A 1989 graduate of Stanford Medical School. Parazynski has logged over 2000 flight hours in a variety of private aircraft. A veteran of four space flights, in 1994, 1997, 1998 and 2001, he has logged over 1,019 hours in space, including 20 hours of spacewalks. He has numerous publications in the field of space physiology and has specialized in human adaptation to stressful environments.

-- Stephanie Wilson, 41, mission specialist. Wilson has a master of science degree in aerospace engineering from the University of Texas. She worked for the Jet Propulsion Laboratory, specializing in the control and modeling of large, flexible space structures. Wilson flew to the International Space Station in July 2006 aboard the Discovery, logging more than 306 hours in space.

-- Doug Wheelock, 47, mission specialist. Wheelock has applied science and engineering degrees from the United States Military Academy in West Point and Georgia Tech. A military test pilot, Colonel Wheelock has logged over 2500 flight hours in 43 different rotary and fixed-wing aircraft before beginning his NASA training in 1998. At NASA, he was also responsible for relations with the Russian Space Agency. Wheelock is scheduled to participate in the mission's three planned spacewalks.

-- Paulo Nespoli, 50, mission specialist. A former Italian special forces officer. He joined the European Space Agency in 1991 in Cologne, Germany. Nespoli began his NASA training in 1998 at the Johnson Space Center in Houston, Texas. He also trained in Star City, Russia, for flying on the Soyuz spacecraft.

-- Daniel Tani, 46, mission specialist. He will replace Clayton Anderson aboard the International Space Station after a six-month stint in orbit. Tani studied mechanical engineering at the Massachusetts Institute of Technology. After completing his astronaut training in 1998, Tani flew to the ISS in December 2001 aboard the shuttle Endeavour. He logged more than 283 hours in space, including more than four hours of spacewalks.

Related Links
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Space Shuttle News at Space-Travel.Com

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