Space shuttle Atlantis is ready to make one last descent to Earth.

亚特兰蒂斯号航天飞机即将最后一次降落回地球。

The orbiter and its crew of four are scheduled to hit the runway at the Kennedy Space Center in Florida just before sunrise on Thursday.

At "wheel-stop", the ship will complete its 13-day mission to the space station; but more significantly, it will close the book on Nasa's 30-year shuttle programme.

Atlantis, like Discovery and Endeavour before it, is being retired¹.

The US space agency is turning to the private sector² for future astronaut transport services, hoping that a number of commercial ventures（合资企业，投机者） will emerge in the coming years to ferry crews to and from the low-Earth orbit.

Atlantis has two opportunities to land on Thursday, with the first timed at 0556 EDT (0956 GMT; 1056 BST). Weather forecasters expect conditions to be near perfect for the attempt.

Officials have resisted calls to target the second opportunity at 0733 and the better light it would afford shuttle fans to see the ship sweep in over Florida's Space Coast.

"We want to stick with what we do normally with our processes and procedures," said LeRoy Cain, the chair of the space shuttle's mission management team.

"Whether it's 40 minutes before sunrise or an hour after, it will be a good landing at Kennedy Space Center. We're going to stick with our plan."

Atlantis undocked from the International Space Station (ISS) on Tuesday. It had delivered some four tonnes of supplies to the platform, including a huge load of food.

Its landing is sure to be wound up with plenty of emotion - not least because it will trigger a big lay-off of contractor³ staff that have supported shuttle operations. More than 3,000 will be let go within days of touch-down.

The programme itself does not officially end for a month, but even then it is likely to take a couple of years to close all activities, such as the archiving of decades of shuttle engineering data.

For Atlantis, its retirement⁴ will be spent as a static（静态的，静电的） display at the Kennedy visitors complex.

Assuming the ship takes the first landing opportunity on Thursday, its career statistics will read 33 flights, 307 days in space, logging 4,848 orbits, for a total distance travelled of 202,673,974km (125,935,769 miles).