Endeavour spent just over 11 days attached to the International Space StationThe ship has spent the past two weeks at the International Space Station (ISS), where it delivered a $2bn particle physics experiment.
Once on the ground, the orbiter will be decommissioned and prepared for public display in Los Angeles.
This will leave just the Atlantis shuttle to make a final flight in July.
Assuming the weather is favourable, Commander Mark Kelly should be able to glide Endeavour to a touch down at the Kennedy Space Center at 0235 local time (0635 GMT).
The ship will then have spent a cumulative 299 days in orbit, travelling more than 197.6 million km (122.8 million miles) during its 25 missions. Endeavour was first launched on 7 May, 1992, as a replacement for the Challenger vessel which was destroyed on launch six years previously.
Nasa is committed to ending its shuttle programme. The vehicles are too costly to maintain and operate, and the agency believes a more affordable approach to getting astronauts to the ISS can be achieved by contracting out their transport to private companies.
The first of these commercial carriers is expected to enter service sometime in the middle of the decade.
Nasa will concentrate its efforts and resources on a Multi-Purpose Crew Vehicle (MPCV) that can go beyond the space station to destinations such as asteroids.
"Endeavour and the space shuttle have been a workhorse for space exploration, building the entire space station and fixing the Hubble telescope, and doing a whole bunch of interesting tasks," said Endeavour pilot Greg Johnson during an in-flight interview on Monday.
"When the space shuttle retires, we're going to lose a lot of capability of moving large payloads out to space; but then that opens the door for new things that are going to come across the horizon. The children out there ought to be inspired that when they get to go to space they'll probably get to go beyond low-Earth orbit, maybe to the Moon, maybe to Mars or beyond."
Endeavour undocked from the station in the early hours of Monday (GMT). The ship's crew of six had gone to the platform to install the Alpha Magnetic Spectrometer (AMS), a seven-tonne detector designed to survey the blizzard of high-energy particles that are fired at Earth from all corners of the cosmos.
Scientists hope that by characterising these cosmic rays, they can learn more about the origins and make-up of the Universe.
Endeavour had also carried up a tray of critical spare parts for the ISS that included cooling, robotic and communications equipment. The four spacewalks conducted by Endeavour crewmembers Drew Feustel, Mike Fincke and Greg Chamitoff, to carry out routine maintenance on the exterior of the platform, were the last in shuttle history.
And by flying on this mission, Fincke, a colonel in the United States Air Force, has broken the record for the most time spent in space by an American, breaking the 377-day mark set by Peggy Whitson.
Much of the media focus on Endeavour's flight has centred on Mark Kelly. He stood down from the mission briefly in January when his wife, Arizona Congresswoman Gabrielle Giffords, was shot in the head by a gunman at a constituency meeting outside a Tucson supermarket.
She made sufficient progress in her rehabilitation to permit Kelly to re-join the mission, and was even present to see Endeavour's launch from Kennedy on 16 May. But Ms Giffords will not be present at the landing.
Atlantis is scheduled to undertake its final mission on 8 July. The vehicle was due to make the five km trip to the launch pad from its assembly hangar late on Tuesday.
The Missouri Department of Public Safety announced Monday that 113 people have been confirmed dead in the Joplin tornado and their next-of-kin notified.
Gov. Jay Nixon directed the Missouri State Highway Patrol Thursday to assume control of notifying next-of-kin.
Sean Kingston's female jet ski passenger tells TMZ Sean was driving "REALLY fast" when they crashed into a bridge this weekend ... and insists she begged him to slow down before the accident.
TMZ spoke with Cassandra Sanchez -- Sean's longtime friend -- who tells us she arrived to Miami Beach with another female friend to ride jet skis with Sean and his buddy on Saturday evening.
Sanchez tells us, "Both jet skis pulled out of the dock at the same time and we were going so fast we just blasted past them. When we turned a corner and crashed ... they were so far behind us they didn't even see us crash."
Sanchez says ... as Sean was racing towards the bridge, she screamed out, "We can't fit under there! Are we going to try and go under there? Sean stop!"
Sanchez tells us ... she believes Sean tried to turn away from the bridge at the last minute ... and
lost control because they were going "REALLY fast."
The next thing Sanchez remembers is waking up in the water in pain. Sanchez says her friends on the other jet ski raced over and tried to help out ... with Sean's buddy trying to position the injured singer so he wouldn't swallow any more water. They all signaled for help until a boat came to the scene to help out.
Sanchez says, "[Sean] was coughing up blood, foam and pink stuff" ... and when he finally opened his eyes, he kept repeating the words, "I'm hurting. I'm hurting"
Sanchez says her ribs and her jaw are still sore -- but overall, she's OK.
As for Sean, Sanchez says "They have a tube down his throat so he can't really talk, but he is lucid and understands what's going on." Sanchez says doctors plan to keep Sean in the hospital for "a couple more weeks."

Apple announced today that it plans to introduce the next generation of its mobile platform, iOS 5, as well as a new cloud service called iCloud at the Worldwide Developers Conference next week on Monday, June 6. This is a highly unusual move for Apple, which normally tries to keep their center-ring announcements secret until the scheduled event.
In a press release, Apple says that iOS 5 will be unveiled alongside iCloud and OS X 10.7 Lion. However, there are no follow-up details on any of the software; the only official tidbit on iCloud is that it is an "upcoming cloud services offering."
There have been unofficial trickles of information on all three products over the last few months. iCloud is rumored to be a "digital locker" type service, not unlike Amazon's recently released cloud services for storing music. iOS 5 is expected to be a major overhaul to the operating system and may include features like over-the-air updates and a new mapping capability, though it will likely not make its way to related devices until this coming fall.
The week before any Apple event is often a time of rabid speculation and digging on the part of news outlets because Apple usually tries so hard to keep its new products under lock and key. Now that Apple is trying to take control of the information flow nearly a week before WWDC starts on June 6, we wonder if we'll see more official details emerge on iOS 5 and iCloud in the next few days.




