Nasa reveals final shuttle dates
Shuttle launch (Esa)
The shuttle is entering its final days
The US space agency (Nasa) has fixed the dates of its last shuttle flights.
The final orbiter to launch before the whole fleet goes into retirement will be Endeavour on 31 May, 2010.
It will be carrying critical spare parts for the International Space Station (ISS) including communications equipment and shielding panels.
By the time the shuttle fleet is stood down, Nasa hopes to have demonstrated the replacement technology with a test flight of its Ares launch vehicle.
The trial mission, called Ares I-X, will be unmanned and will check out the key components needed to loft the new Orion crew carrier which is expected eventually to take astronauts back to the Moon.
The dates of the remaining shuttle flights are provisional and could change. As has been the case throughout the orbiters' history, a technical hitch or unfavourable weather conditions can always push back a flight by several days.
The next shuttle mission on 8 October this year will go to the Hubble Space Telescope to give it one last service.
The outstanding orbiter flights are then dedicated to finishing construction of the ISS, and stocking the platform with critical auxiliary components.
Cupola
The Cupola will give astronauts an all-round view of the station
The last big structural items that need to be lofted include the fourth, starboard "backbone" segment and the fourth set of solar arrays. These are scheduled to fly on Discovery on 12 February next year.
The last major European-built component to go up on a shuttle - on Endeavour on 10 December, 2009 - will be the Cupola window.
This observation module was constructed by Alenia Spazio (now incorporated into Thales Alenia Space) in Turin and is currently stored in the Space Station Processing Facility at the Kennedy Space Center.
The 1.8-tonne Cupola will act like a control tower for the ISS. Its trapezoidal windows will give astronauts a panoramic view of the platform.
They will enter it to observe exterior operations, using controls in the module to guide the robotic arm system as it makes repairs or moves around supplies.
"Astronauts are going to love it and they are going to spend every available minute they possibly can in there, just because the view will be so spectacular," explained Jim Flemming from Boeing (the aerospace company did the early concept work on Cupola).
Ares 1-X (Nasa)
Nasa will begin test flights of post-shuttle technology next year
"It will also provide really good photography of the Earth. The glass is good enough for that. The astronauts take a lot of pictures and for the public at large, that's a fantastic benefit," he told the BBC when we visited the Processing Facility in February.
With the shuttle retired, the ISS will rely on the European ATV, Japanese HTV and Russian Progress craft for logistics.
Nasa is backing commercial operators to take up at least some missionsin the future.
Before the US returns to the ISS with Orion, it is expected the station will have been visited by the Falcon/Dragon launch system now in development with SpaceX.
The Californian company claims its totally reusable system will dramatically reduce the cost of low-Earth orbit operations.
. No external boosters or rockets. 
