After 13-day long successful mission that enabled it to deliver the final US components of the International Space Station, the space shuttle Discovery was due to touch down at the Kennedy Space Centre in Florida for the final time on Wednesday.

As NASA begins to retire its ageing shuttle fleet, the spacecraft, which is ending 27 years of service, was due to land at 11:58 am local time after delivering the extra room along with supplies and equipment, including a human-like robot, known as Robonaut 2 (R2), the first such robot ever sent to space.

A pair of Discovery astronauts completed two spacewalks to conduct repairs on the outside of the ISS.

NASA has two chances to land Discovery in Florida on Wednesday and the weather is expected to cooperate.

If Discovery misses the first opportunity, the second window opens up at 1:34 p.m., NASA officials said.

After that, the next chances to land would come on Thursday.

If foul weather or other problems do delay the landing to Thursday, a backup runway could come into play.

Kennedy will remain the number one option, mission managers said, but Discovery could also be shunted out to California’s Edwards Air Force Base.

Another backup runway is also available at White Sands Space Harbor in New Mexico, should it be needed, they added.

But forecasts call for good conditions in Florida, so chances of a touch down at Kennedy are good, officials said.

It was originally to have occurred four months ago, but the shuttle was plagued by multiple delays after cracks were discovered in the spacecraft’s external fuel tank.

It took NASA several months to pinpoint and fix the cause of the cracks.

The oldest shuttle in the fleet, Discovery has spent a year in orbit and logged many spaceflight firsts.

Now it will be the first of the three remaining shuttles to be retired and head to a museum.

It was the first shuttle to return to flight after both the shuttle Challenger and Columbia accidents; launched the trailblazing Hubble Space Telescope; made the first US rendezvous with the Russian Mir space station; and made the first and last shuttle trips to rotate crews on the International Space Station (ISS).

As Discovery prepares to return to Earth for good, mission managers praised the orbiter and her crew for a great mission so far.

“We couldn’t be more pleased,” said LeRoy Cain, NASA’s mission management team chairman.

“The team just did an outstanding job. The entire space shuttle system just performed outstanding on this entire mission.”

Construction began in 1979 on Discovery, which blasted off into space for the first time in 1984.

It has made more flights than any other shuttle and carried more crew members.

NASA officials have largely focused on the ongoing mission rather than the history Discovery is about to make, but occasionally mention that they will be sad to see the shuttle end its long career.

“It’s bittersweet and, quite frankly, sad knowing when we land that’ll be the end for this vehicle,” commander Steve Lindsey said last week in a press conference from space.

Johnson Space Centre Director Michael Coats, who flew the first Discovery mission, said on NASA television that the space agency can look back with pride on the long history of the shuttle.

“It will take the public a few years to realize the capabilities the shuttle actually had,” he said, noting the space station could not have been built without the shuttle fleet’s heavy lifting capability.

“There’s nothing that’s going to come even close to that” being developed, he said.

NASA plans to shift routine ferrying of astronauts aloft to commercial spaceflight providers and focus its attention on building long-range craft to eventually take people to Mars.

In the short term, the agency must rely on Russian Soyuz vehicles to carry astronauts aloft.

NASA has two more shuttle missions planned Endeavour’s STS-134 flight in April, and the program’s swan song, Atlantis’ STS-135 flight in June.