The space shuttle Endeavour and its crew are scheduled to return to Earth early Wednesday morning, completing NASA's second-to-last shuttle flight. There is only one more flight on the schedule, by the shuttle Atlantis -- the end of a 30-year program.
Endeavour undocked from the International Space Station late Sunday. The entry flight control team will evaluate weather conditions at the landing site at Merritt Island, Fla., before giving the approval to land, NASA said.
The 25th and final flight for Endeavour also marks the last flight for the six men flying Endeavour. The astronauts, all veterans of previous flights, are wrapping up a 16-day mission, where they added the last major components to the U.S. section of the International Space Station.
Endeavour's crew includes Cmdr. Mark Kelly; pilot Greg Johnson; spacewalkers Mike Fincke, Drew Feustel and Greg Chamitoff; and European Space Agency astronaut Roberto Vittori, who's handling robotics.
"To see the horizon out there, with all that hardware beneath you and to understand what we've done as a nation and as a world to build that international space station; it's spectacular," astronaut Feustel said.
Spacewalker Fincke, who has spent months living on the space station in years past, now holds the U.S. record for time in space, at 380 days.
"I hope my record is soon broken," Fincke said.
Endeavour delivered a $2 billion cosmic ray detector, called Alpha Magnetic Spectrometer-2 (AMS), which will remain mounted on the space station for the next decade. The cosmic ray detector is searching for antimatter and dark matter, which scientists hope will shed light on the origins of the universe.
"Understanding what the universe is -- the universe we live in, how we all got here, how it was formed -- these are fundamental questions, and this is what AMS is going to be trying to understand for us," Chamitoff said.
The mission has so far been a complete success for NASA.