WASHINGTON, July 29 (Xinhua) -- Space shuttle Endeavour's astronauts inspected its heat shield one more time Wednesday with lasers and cameras as they begin to set their sights on a Friday landing, NASA said.
Endeavour's thermal protection system was cleared for landing earlier in the flight. This late inspection will ensure that there has been no impact damage from micrometeoroids or space junk during its docked operations or fly-around of the station.
A preliminary look at the images beamed down found nothing amiss, and everything was on track for Friday's planned landing, according to NASA.
The U.S. space agency also said Wednesday that there are two landing opportunities at NASA's Kennedy Space Center in Florida at 10:48 a.m. (1448 GMT) and 00:23 p.m. EDT (1623 GMT) on Friday.
NASA will evaluate weather conditions at Kennedy before permitting Endeavour and its crew to land. If weather prevents a return to Kennedy on Friday, the backup landing site at Edwards Air Force Base in California will be activated Saturday for consideration as well.
Endeavour blast off on July 15 from Kennedy Space Center after five delays, on a trip to the International Space Station (ISS). Its mission featured five spacewalks and completed construction of the Japan Aerospace Exploration Agency's Kibo laboratory.
Astronauts also replaced six batteries for the ISS and performed a number of "get ahead" tasks, including tying down some cables and installing handrails and a portable foot restraint to aid future spacewalkers.
Seven more shuttle flights are planned over the coming year to complete the construction of the ISS. The launch of the next shuttle, Discovery, to the ISS is scheduled for the end of next month.