Atlantis astronauts wrap up spacewalk

HOUSTON (Reuters) - Two shuttle Atlantis astronauts wrapped up a spacewalk on Friday to install a solar observatory and a science experiment on Europe's space lab.

The Columbus module, the European Space Agency's $1.9 billion permanent space laboratory, was launched aboard NASA's Atlantis last week and connected to the International Space Station (ISS) on Monday.

As preparations began for the shuttle's return on Wednesday, NASA said it was readying its landing sites at both the Kennedy Space Center in Florida and Edwards Air Force Base in California.

The U.S. military is eager to land the shuttle by Wednesday so it can proceed with a planned attempt to shoot down a disabled spy satellite with a missile.

NASA prefers to land the shuttle at Kennedy, its home port and launch site, because of the high cost of transporting the spacecraft from California. The agency often does not open Edwards until the second day of landing opportunities if weather prevents a Florida landing on the first day.

During Friday's third and final outside excursion of Atlantis' nine-day visit to the space station, lead spacewalker Rex Walheim and partner Stanley Love picked up a broken gyroscope and did some inspection work on a hand rail outside the airlock.

They did not have time during the nearly 7 1/2-hour spacewalk to examine a contaminated solar wing joint that has mired station operations since October. It has been inspected on previous outings.

NASA needs to fix the joint so the station can reach full power before the arrival of a large Japanese laboratory, known as Kibo, later this year. Replacing the faulty equipment will require four to five spacewalks on later missions.

The solar observatory installed on this mission contains instruments that will, among other things, measure aspects of the sun's energy and help scientists decipher the impact of solar activity on Earth's climate.

The other facility attached to Columbus' hull will be used to conduct a range of space-related experiments. These include exposing lichen and fungi to space conditions for about 1 1/2 years to test the limits of their survival.

Another will evaluate the effects of space on different materials that may be used on spacecraft in low Earth orbit.

"The aim is to improve components and materials for spacecraft design," Alan Thirkettle, the ISS program manager for the European Space Agency, told Reuters.

He later told a news briefing at the Johnson Space Center in Houston that they would start getting data from the solar observatory before the end of February.

The agency has nine construction missions remaining to complete the $100 billion outpost and two resupply flights planned before the shuttle fleet is retired in 2010.

(Editing by Stacey Joyce)