The shuttle Atlantis has landed safely in Florida, completing a successful mission to install Europe's first space laboratory.
Atlantis touched down at Cape Canaveral at 2.07pm Irish time, bringing home seven astronauts following a 13-day mission to the orbiting International Space Station.
NASA already has its next spaceship at the launch pad for an 11 March flight to continue assembling the ISS.
Atlantis' return frees the US Navy to fire a missile as early as tonight at a falling spy satellite which is loaded with toxic rocket propellant.
The US military says the fuel could pose a hazard to populated areas and that destroying the satellite just before it re-enters Earth's atmosphere increases the chance that debris will fall harmlessly into the ocean.
The satellite was launched in December 2006 and failed shortly after reaching orbit.
Atlantis needed to land before the military operation to avoid flying through satellite wreckage as it returned to Earth and risk heat shield damage similar to what triggered shuttle Columbia's destruction in 2003.
The space station, which orbits more than 320 km above the planet, would not be endangered by the satellite debris, which is expected to be pulled into Earth's atmosphere and incinerated within a few days after the spacecraft is destroyed.
The operation, likewise, is not expected to impede NASA's plans to return to the station with shuttle Endeavour next month to install the first piece of Japan's three-part Kibo laboratory complex, where a berthing port opposite Europe's newly arrived Columbus module awaits.
