( dpa )- The crew of Space Shuttle Atlantis was running tests and preparing for a return to Earth that is set for Wednesday.
The shuttle will have its first opportunity to land at Kennedy Space Center in Florida at 1407 GMT and the weather forecast was reported as favourable.
US space agency NASA will be rushing to bring the shuttle down wherever possible due to the US military's plans to shoot down a satellite that is hurtling towards Earth. That action is could happen as early as Wednesday night. NASA officials said they were preparing the landing site at Edwards Air Force Base in California just in case.
The shuttle undocked from the International Space Station Monday after nine days of helping set up the Columbus laboratory - Europe's long-awaited contribution to the project that Atlantis brought up after a four-year delay.
Before departure, the crew one last time checked the fragile heat shield that protects Atlantis during reentry to rule out any defects.
Astronauts on Tuesday tested control surfaces and thrusters used to manoever the shuttle as it re-enters the planet's atmosphere. NASA said that four aft thrusters on the shuttle were inoperable due to a heater that failed overnight, but officials said the thrusters would not be needed in the return.
Crew member Daniel Tani was also being prepared Tuesday for the rigours of a return to Earth after a four-month stint in the weightless atmosphere of the ISS.