Astronauts on board the space shuttle Discovery were Thursday preparing to maneuver the craft away from a piece of debris, ahead of a bid to return to Earth which may be thwarted by bad weather.
The unidentified piece of debris apparently drifted away from the shuttle during a space-walk outside the space station on Saturday.
An evasive maneuver was planned for 1602 GMT to prevent the shuttle astronauts from speeding too close to the debris, mission control said.
The "mystery object" was on a course that would bring it close to the shuttle over 11 consecutive orbits of the Earth.
Although stormy weather was forecast at the Florida landing site, two touchdown chances had been earmarked at 2205 GMT and 2342 GMT at NASA's Kennedy Space Center.
Discovery's return marks the end of a 13-day mission to the International Space Station during which the crew installed new scientific equipment, overhauled the station's cooling system and gathered up external experiments.
But forecast rain showers and thunderstorms may force the US space agency to delay the shuttle's return to Earth, although it is equipped with enough provisions to remain in orbit through Sunday.
If a wave-off becomes necessary, NASA will consider making available a runway at Edwards Air Force Base, California on Friday.
"The weather in Florida at this time of year is always a little iffy," Discovery commander Rick Sturckow said late Wednesday.
"We will make sure the crew and Discovery are ready and then we will wait for Mission Control to make the call. The worst that can come out of it is that we have another day in space, which is a great deal."
On Wednesday, NASA mission managers finished an evaluation of the shuttle's heat shielding, concluding the fragile thermal barrier was in good shape for the high velocity descent to Earth.
Sturckow and Discovery pilot Kevin Ford tested the spacecraft's steering and communications systems as well, finding no problems.
It was during the steering tests, that one of the astronauts noticed and captured photographs of a three to four-inch-long strip of material floating away from Discovery.
Although unable to positively identify the ribbon line object, Mission Control was able to determine it did not originate from the heat shielding.
"Everything checked out very clean," Richard Jones, the NASA flight director who will supervise landing activities from Mission Control, told reporters. "The vehicle is ready to come home."
Discovery returns to Earth with American astronaut Tim Kopra, who is ending a 57-day mission to the space station, and just over 5,200 pounds of research gear, discarded equipment and trash.
"This experience has completely exceeded anything I thought it would it would be like, just in sights and sounds, the experiences," said Kopra. "It's been absolutely phenomenal."
He was replaced on the station by Discovery astronaut Nicole Stott, who is scheduled to remain aboard the outpost with five Russian, European and Canadian astronauts through late November.
Source: AFP American Edition
