Weather stymies shuttle landing again, re-try Sunday

CAPE CANAVERAL, Florida (Reuters) - Rainstorms and clouds over Florida forced the space shuttle Atlantis to cancel its attempted homecoming for a second day on Saturday, and NASA said it would try to bring it back to Earth on Sunday.

Atlantis' seven crew members, winding up a 12-day servicing mission that repaired and upgraded the Hubble Space Telescope, had already been obliged to stay in orbit for an extra day on Friday as the volatile weather shut off the landing site.

Downpours and dark clouds rolling in over the Kennedy Space Center in Florida again on Saturday, leading NASA flight directors to decide to hold off the landing until Sunday, when it was hoped weather conditions would improve.

"The weather at the Kennedy Space Center (in Florida) has not cooperated ... we are waiving for the day," a NASA official at Houston Mission Control said.

Too much rain or too many clouds violates the space agency's criteria for a safe landing.

NASA has four scheduled opportunities on Sunday for Atlantis to land either at the Kennedy Space Center in Florida or at the alternate touchdown site at the Edwards Air Force Base in California.

Atlantis was well equipped with extra supplies as a safety precaution on its mission to Hubble, and has enough supplies to stay in orbit until Monday.

The backup landing site at Edwards Air Force Base in California's Mojave Desert is prepared by NASA in the event that Florida's notoriously variable weather frustrates landing attempts at the shuttle's Kennedy home spaceport.

NASA would prefer to land the shuttle at Kennedy in Florida because landing in California costs more than $1 million. It requires the cumbersome and risky transfer of the shuttle on top of a jet carrier aircraft to Florida for its next launch.

As NASA focused on the Atlantis landing on Saturday, the White House announced President Barack Obama would nominate Charles Bolden, a 62-year-old four-time space shuttle astronaut and retired Marine major general, to serve as the space agency's new administrator.

SHUTTLE FLEET TO RETIRE IN 2010

The scheduled shuttle landing opportunities for Sunday are 10:09 a.m. EDT and 11:48 a.m. EDT at the Kennedy Space Center in Florida, and 11:40 a.m. EDT and 13:17 p.m. EDT at the Edwards Air Force Base in California.

NASA is trying to finish up eight flights on the shuttle's manifest before the fleet is retired by the end of 2010. It is targeting its next shuttle mission for launch in three weeks.

Shuttle Endeavour, which was on standby as a rescue vehicle for the Atlantis crew, is scheduled to deliver an outdoor porch for the Japanese laboratory on the International Space Station.

NASA wanted the standby rescue capability since the Atlantis crew on their mission to the Hubble observatory could not reach the station if their ship was too damaged for the return flight through the Earth's atmosphere for landing.

NASA has been worried about possible heat shield damage to shuttles since the 2003 loss of shuttle Columbia. All seven crew members died when Columbia disintegrated upon re-entry into the atmosphere.

The Atlantis crew had used laser imagers to inspect their ship's heat shield after reaching orbit. NASA determined the shuttle is in good shape for landing.

On their mission, the astronauts conducted five consecutive days of spacewalks to refurbish the highly productive Hubble telescope, which has been in orbit since 1990.

Hubble was outfitted with a new panchromatic wide-field camera that is expected to be able to image objects formed about 500 million years after the birth of the universe.

The Atlantis astronauts also left Hubble with a new light-splitting spectrograph to investigate the chemical composition of gas and dust between the galaxies.

Astronomers are curious to learn how early structures like galaxies came into existence.

The first images from the rejuvenated Hubble are expected in September.

(Editing by Pascal Fletcher and Paul Simao)