Space Shuttle Discovery to Land Today

CAPE CANAVERAL, Fla. - All that stands between six astronauts in space and a warm Florida landing are about 200 miles (321 kilometers) and the hint of rain.

NASA's STS-121 astronaut crew and their space shuttle Discovery up in orbit are due back on Earth at 9:14 a.m. EDT (1314 GMT) today, when the spacecraft's new tires are expected to touchdown on Runway 33 here at the Kennedy Space Center (KSC) landing facility.

"We've inspected the vehicle and we understand the [heat shield] more than we have on any other mission," NASA's reentry flight director Steve Stitch told reporters Sunday. "The vehicle is totally clean for reentry."

Discovery's anticipated landing comes after a busy 13-day mission that not only completes NASA's return to flight tests, but also increased the crew size of the International Space Station (ISS), readied the orbital lab for future construction. The mission marked NASA's second shuttle flight since the 2003 Columbia accident.

"Hopefully the weather will be great in Florida tomorrow," STS-121 pilot Mark Kelly said Sunday.

Watching weather

All eyes will be on the weather this morning to ensure that Discovery won't run into rain or other unfavorable conditions.

Mission controllers are hoping for clear skies, though forecasts predict that some rain showers may creep too close to a 30-mile (48-kilometer) zone around Discovery's landing site. The space shuttle cannot land in rain because it could damage the thousands of black ceramic tiles that protect the orbiter's belly from the searing heat of reentry.

"My experience that at the Kennedy Space Center, it's always a challenge," Stitch said of Florida's weather on Sunday. "I think we have a pretty good shot at getting into Kennedy tomorrow."

If all goes well, Kelly and STS-121 commander Steven Lindsey will fire Discovery's engines at about 8:07 a.m. EDT (1210 GMT) to slow the spacecraft and begin its hour-long drop toward Earth. That maneuver would deliver Discovery and its six-astronaut crew to a 9:14 a.m. EDT (1314 GMT) landing after 202 orbits around Earth.

Should rain cloud that initial attempt, Stitch and his flight control team could order Discovery's crew to hold off for about 90 minutes, though the forecasts call for deteriorating weather conditions for a second pass.

That would call for the crew to make one last circle around Earth before firing Discovery's engines at 9:43 a.m. EDT (1343 GMT) for a landing at 10:50 a.m. EDT (1450 GMT), NASA said.

Stitch said that Discovery's crew will only attempt to land at KSC today since the site is home to NASA's three-shuttle fleet.

A KSC landing would minimize the amount of time needed to once-more ready Discovery for flight, first to serve as a potential rescue ship - if needed - for NASA's STS-115 shuttle mission to slated for an Aug. 28 launch, then as the primary vehicle for the STS-116 mission to the ISS in December.

"We try to get into Kennedy because it helps us get ahead a little bit on our turnaround," Stitch said. "That's where all our maintenance facilities are, so we like to land there if we can safely."

If Discovery does not land today, flight controllers will activate alternate landing sites at Edwards Air Force Base in California's Mojave Desert and Northrup Strip at New Mexico's White Sands Space Harbor with the aim of bringing the shuttle home by Wednesday at the latest.

Stitch said that KSC will be the prime landing site for any Tuesday attempt, with Edwards as a backup should the whether go foul. Northrup Strip is reserved only for the worst-case scenario of poor weather at both KSC and Edwards, he added.

Space shuttle landings at Edwards or Northrup Strip typically require about seven extra days, and an additional $1 million to transport an orbiter back to its hangar at KSC.

NASA officials said shuttle workers already have a challenging schedule of about 110 days to ready Discovery for its STS-116 launch on Dec. 14, with only five extra days of padding in case of delays.

"The standard joke is that I asked Steve Lindsey to make sure that he brought home my vehicle in good condition, and that he didn't prang it on the runway," NASA astronaut Mark Polansky, NASA's STS-116 mission commander, told SPACE.com before today's landing attempt. "He promised to do the best he could."

Discovery's planned landing activities will be broadcast live on NASA TV beginning with crew wakeup at 1:08 a.m. EDT (0508 GMT). You are invited to follow the progress of Discovery's STS-121 crew via SPACE.com's NASA TV feed, which is available by click here.

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