The shuttle Discovery has been cleared to return to Earth, but poor weather over the Kennedy Space Center may force it to an alternative landing site. Nasa controllers have Edwards Air Force Base, in California, and White Sands Space Harbor, in New Mexico, on standby to receive the vehicle. If the rain and clouds lift at Kennedy, Discovery's first landing opportunity is at 2056 GMT (1556 local time). Nasa is prepared to delay the return to Saturday if needs be.
ESA TV coverage of STS-116 mission on landing day - 22 December
22 December 05:00 - 05:30 GMT Flight Day 13 Highlights of Mission STS-116
The day before landing is packed with activities to prepare the Orbiter for its atmospheric entry: stowage, check-outs, procedure reviews.
22 December 19:00 - 23:00 GMT LIVE: Landing of Shuttle Discovery
NASA will activate three landing sites in the US for the landing: Kennedy Space Centre in Florida, Edwards Air Force Base in California and White Sands Air Force Base in New Mexico. Flight rules say the Shuttle must land at the first opportunity where there are acceptable landing conditions, both technically and weather-wise. Weather conditions do not look optimal neither for Florida nor for California. The timeline of events is as follows - covered by a four-hour rebroadcast of NASA-TV:
19:30 GMT (approx) Latest moment to decide not to land at the first possible touchdown at KSC, due to bad weather
20:56 GMT First possible touchdown at KSC
21:00 GMT (approx) Latest moment to make a decision on which of all three landing sites the Orbiter will touch down
22:26 - 22:31 GMT Possible touchdowns at the three landing sites
In case of a landing at White Sands, the amount of live landing coverage is not sure as this site has limited television capabilities. There are further landing opportunities at approx 00:00 GMT and 01:36 GMT which will however not be covered live. An ESA-TV landing summary will be transmitted on 23 December at 07:00 GMT - a separate mailing will be made in the afternoon of 22 December.
While the shuttle Discovery's astronauts get set for their homecoming, NASA managers are facing a series of complicated trade-offs about where to land the spacecraft.
The space shuttle Discovery has undocked from the International Space Station (ISS) after an eight-day stay on the orbiting outpost. Early on Tuesday, astronauts fixed jammed solar panel on the ISS during an unscheduled fourth spacewalk. A US astronaut on the space station has switched places with a member of the seven-person Discovery crew and will travel back to Earth on the orbiter. Discovery detached from the space station at 22:10 GMT.