July 28, 2005 - 11:35 PM

Discovery's crew readies for 2nd try at landing

By Deborah Zabarenko

CAPE CANAVERAL, Florida (Reuters) - Astronauts aboard space shuttle Discovery, prevented from returning to Earth by bad weather on Monday, prepared for a second day of landing opportunities to conclude the first shuttle mission since the 2003 Columbia disaster.

"We sure hope we get our feet on the ground today," astronaut Wendy Lawrence told mission controllers in Houston after the crew's evening wake-up call.

Flight controllers decided against two landing opportunities on Monday at the Kennedy Space Center in Florida because of unpredictable weather near the landing strip.

Similar weather was forecast for Tuesday's two landing opportunities in Florida, and NASA flight directors offered the option of landing in California and New Mexico.

NASA has several chances to land the shuttle on Tuesday, including at 5:07 a.m EDT (10:07 British time) or 6:43 a.m. EDT in Florida and at 8:12 a.m. EDT and 9:47 a.m. EDT at the primary backup site in California.

Discovery also could land at the secondary backup site, the White Sands Test Facility in New Mexico, at 6:39 a.m. EDT or 8:13 a.m. EDT.

Barring emergencies, NASA will only land Discovery if there is at least 5 miles (8 km) of visibility for the approach to the runway and no rain, lightning or thunderstorms within 35 miles (56 km).

"It's not tomorrow or bust, that's for sure," said NASA spokeswoman Laura Rochon in Houston, adding that Discovery had enough fuel and supplies to stay in orbit for a few more days. "We fully expect to land tomorrow or Wednesday."

Shuttle commander Eileen Collins planned to tweak Discovery's orbit slightly so that if the shuttle had to land in California, it would not fly over Los Angeles. After the Columbia accident, which showered debris over Texas and Louisiana when the ship broke apart, NASA decided to avoid flying over heavily populated areas.

BACKUP SITE

Shuttle program deputy manager Wayne Hale said NASA also would staff its second backup landing site in New Mexico.

The landing will bring to a close NASA's first shuttle mission since Discovery's sister ship, Columbia, was destroyed on February 1, 2003, 16 minutes from landing.

NASA did not know that the ship's wing had been critically damaged during launch by a piece of falling debris. As Columbia plowed through the atmosphere 16 days later for landing, superheated gases blasted into the hole, ripping the ship apart and killing all seven astronauts.

After the accident, NASA developed on-orbit laser imaging tools and inspection techniques, which were tested during Discovery's flight. They determined that an unplanned spacewalk was needed to make a minor but unprecedented repair to the ship's heat shield.

But the biggest problem on the mission occurred at launch when a chunk of foam almost as large as the one that damaged Columbia flew off Discovery's fuel tank. Columbia's wing damage was caused by a piece of foam insulation that fell off the tank during launch.

In Discovery's case, the foam did not strike the ship but NASA suspended shuttle flights until the problem was solved.

Discovery spent nine days at the International Space Station on a servicing and resupply mission. In addition to replenishing the station's pantry, water supplies and other gear, the shuttle delivered a new gyroscope to the outpost and revived a second failed device, restoring full service to the steering system for the first time in more than three years.