NASA counted down to a Monday launch of the space shuttle Discovery, with all systems ready for a mission that will put more women in orbit than ever before.
Discovery's planned arrival at the International Space Station is tentatively scheduled for Wednesday and will be one of the final missions for the shuttle program, which will be shuttered later this year. It is the first shuttle mission with three female crew members and will also mark a first in space, with four women in orbit.
The seven Discovery astronauts were safely strapped in, wearing their bulky, orange launch-and-entry suits. The side hatch was closed and sealed for Discovery to blast off from Launch Pad 39A at the Kennedy Space Center in Cape Canaveral, Florida.Its launch was set for 6:21 am (1021 GMT).
"Weather is excellent and expected to remain that way during this final hour before launch," the US space agency said. Discovery's external fuel tanks were filled with about 500,000 gallons (1.9 million liters) of chilled liquid oxygen and liquid hydrogen at Launch Pad 39A. The propellants will remain completely full until countdown is completed. The "tanking" operation ended at 12:21 am, a little less than three hours after it began.
"There are no technical issues that we are working on at this time of major concern, everything remains a go," NASA spokesman Mike Curie said in a statement. There was an 80 percent chance of favorable weather conditions. The only concern was morning fog.
It will be the second space shuttle launch for NASA this year. After this flight, only three more are planned before all three remaining US manned orbiters are retired at the end of 2010, ending 30 years of service. The first shuttle flew in April 1981.
During the 13-day mission, Discovery and its crew will deliver nearly eight tonnes of cargo, including spare bunks for the occupants of the space station, a large tank of ammonia coolant and seven racks filled with science experiments. American Tracy Caldwell Dyson arrived at the orbiting space station on Sunday aboard a Soyuz spacecraft with two Russian cosmonauts.
Joining Dyson from Discovery will be mission specialists Dottie Metcalf-Lindenburger, 34, a former high school science teacher; Stephanie Wilson, 43, a veteran of two shuttle missions; and Naoko Yamazaki, 39, an astronaut with the Japanese space agency since 1996.
Rounding out the Discovery crew are mission commander Alan Poindexter, 48; co-pilot Jim Dutton, 41; mission specialist and spacewalker Rick Mastracchio, 50; and fellow spacewalker Clay Anderson, 51.
Among the gear being hauled into space is a freezer to preserve samples of blood, urine, saliva, plants or microbes used in micro-gravity experiments and then analyzed later back on Earth.
Discovery also will be carrying an exercise machine designed to study the effects of micro-gravity on the body's musculoskeletal system. Muscles can atrophy during long sojourns in space so astronauts have to take care to exercise regularly.
The supplies, racks and other gear are packed into a pressurized Italian-built module named Leonardo, carried in the shuttle's bay.