Space shuttle begins descent for California landing

EDWARDS AIR FORCE BASE, Calif June 22 (Reuters) The US space shuttle Atlantis broke orbit today to begin a fiery descent through the Earth's atmosphere for a landing in California's Mojave Desert.

Flying upside-down 220 miles (354 km) over the Indian Ocean, Atlantis commander Frederick Sturckow fired the shuttle's twin maneuvering engines to drop out of orbit and begin an hourlong glide to Edwards Air Force Base, its backup landing site.

Touchdown was scheduled for 0119 hrs IST.

Flight directors had hoped skies would clear for one of two landing opportunities at the Kennedy Space Center in Florida today, but dense clouds and rain prevented that.

''We just couldn't quite get comfortable with KSC,'' astronaut Tony Antonelli from Mission Control in Houston radioed to Atlantis commander Frederick Sturckow.

The shuttle has been in orbit two weeks on a construction mission to the International Space Station, a 100 billion dollars project of 16 nations that is a little more than half finished.

The US space agency had planned to end its first shuttle mission of the year yesterday but the spacecraft and its seven astronauts were told to stay aloft an extra day due to typical summer thunderstorms at Kennedy.

NASA would have preferred to land at Kennedy to save the expense and time required to piggyback the shuttle back across country on a modified Boeing 747.

The shuttle is barred from landing in rain due to potential damage to the thousands of black ceramic tiles that protect its underside from the searing heat of re-entry through the atmosphere.

The shuttle carted a third pair of power-producing solar wing panels to the space station and its crew conducted four spacewalks to install them, fold up another older wing that will be moved to a new location and install equipment needed to prepare for the arrival of additional research laboratories.

The astronauts also were called upon to repair a hole in the heat shield on Atlantis, which arrived in orbit with a corner of an insulating blanket torn loose.

NASA has been meticulous about scouring the shuttles for damage once they reach orbit since a heat shield failure triggered the destruction of the shuttle Columbia in 2003 and the deaths of seven astronauts.

The crew also delivered a new astronaut to the station.

Clayton Anderson replaced station flight engineer Sunita Williams, who is returning home aboard Atlantis after a record-breaking six months in space.

Williams surpassed Shannon Lucid's 188-day mission for the longest spaceflight by a woman.

NASA needs to fly 12 more construction missions to finish building the station before the end of 2010, when the shuttle fleet is due to be retired.

The US space agency also would like to squeeze in two resupply missions and a final servicing call to the Hubble Space Telescope.

Atlantis' mission at the space station was overshadowed by a major computer breakdown in the Russian modules that could have led to the station being temporarily abandoned. Work was continuing on the station computers.

REUTERS RKM BST0038