Shuttle reaches launch pad for May 31 liftoff

HOUSTON (Reuters) - Space shuttle Discovery reached its Cape Canaveral, Florida, launch pad on Saturday in preparation for a May 31 liftoff to place a huge Japanese research complex on the International Space Station.

With the shuttle in position, NASA will hold a practice launch countdown with the seven-member crew next week. The mission is the third of five planned for this year.

NASA has 10 shuttle flights remaining to the $100 billion space station before the fleet is to be retired in 2010. The U.S. space agency also plans a final servicing call to the Hubble Space Telescope this fall.

The shuttles, which were designed in the 1970s, are being retired due to safety issues and to pay for the development of new spaceships that are capable of traveling to the moon as well as low-Earth orbit.

NASA estimates the country will need to depend on Russian space transports to ferry station crewmembers to and from the station for about five years while the new ships are under construction.

Discovery's crew, led by Mark Kelly, includes five first-time fliers and two veterans. Kelly has made two previous spaceflights and lead spacewalker Michael Fossum, has flown once.

The crew includes Japan's Akihiko Hoshide, who will oversee the initial setup of Kibo, the Japanese Aerospace Exploration Agency's primary contribution to the space station. Also aboard will be pilot Ken Ham, spacewalker Ron Garan, Karen Nyberg and space station flight engineer Greg Chamitoff, who will replace Garrett Reisman as a member of the live-aboard space station crew.

NASA delivered a storage compartment for Kibo during its last shuttle mission in March. A final segment of the elaborate lab, an exposed back porch for microgravity research experiments, is due to arrive next year.

(Editing by Sandra Maler)