CAPE CANAVERAL, Fla. – Mission Control on Sunday gave the green light for Discovery to attempt landing Monday, concluding that inspections of the space shuttle's protective skin showed no signs of damage.
The decision was made after NASA engineers reviewed images from an inspection of the shuttle's wings and nose cap, conducted Friday and Saturday by Discovery's crew using sensors at the end of a 50-foot boom attached to a 50-foot robotic arm.
The inspection was to make sure there's never a repeat of the Columbia disaster, in which seven astronauts were killed during re-entry to Earth's atmosphere because of a damaged shuttle wing.
"Is the vehicle cleared for entry?" Steve Lindsey, Discovery's commander asked after hearing the news.
"That's affirm. I'm being told I can use that word. You are cleared for entry," astronaut Steve Frick in Mission Control radioed back.
NASA managers were keeping an eye on the weather as showers threatened to come within 30 miles of the Kennedy Space Center's 15,000-foot runway on Monday morning.
NASA was going to attempt a landing only at the Florida space center on Monday but said it would consider the backup landing site at Edwards Air Force Base in California if forced to postpone because of weather. The shuttle must land by Wednesday.
"The clouds shouldn't be an issue; however, there's still a chance of showers," Frick told Lindsey. "We'll be looking real close at that."
Discovery will try to land at 9:14 a.m. or 10:50 a.m. EDT Monday, completing a successful 13-day mission that took supplies and an extra crew member to the international space station and allowed spacewalkers to repair a vital rail car on the station.
Mission Control also told Discovery that a leaking unit that powers hydraulic systems used for steering and braking shouldn't pose a problem during landing.
Engineers were not sure whether it had been leaking harmless nitrogen or flammable hydrazine and had considered burning off the fuel and shutting down the unit before landing to eliminate any fire hazard — something NASA has never done before. The spacecraft needs only one power unit to land.
Without a third power unit, Discovery's landing gear would have to be deployed by explosive charges rather than the hydraulics system, and stricter weather requirements would be implemented for the shuttle's landing at the Kennedy Space Center.
But early testing results on the unit Sunday morning showed no problems.
"We saw normal fuel usage, normal parameters," Mission Control radioed Steve Lindsey, Discovery's commander.
Lindsey responded, "OK. Great news."
The crew also practiced firing jets that will be used during Discovery's re-entry into Earth's atmosphere, and Lindsey and pilot Mark Kelly practiced landing on a computer simulator.
Later in the day, the crew members had a series of television interviews scheduled.
They awoke Sunday to a recording of The Cure's "Just Like Heaven," chosen by astronaut Piers Sellers' family. Sellers told Mission Control the song reminded him of "the wild, happy, drinking-beer years of my youth."