By Jonathan Amos
Science reporter, BBC News, Turin
Node 3 will now be flown to the US
Europe has rolled out its last major module for the space station.
The cylindrical Node 3 - to be known as "Tranquility" - was constructed by Thales Alenia Space in Turin, Italy.
Once attached to the station, it will house life support gear as well as being home to the Cupola, a giant "bay" window that was also built in Europe.
Node 3 will be shipped shortly to the Kennedy Space Center in the US, from where it will catch a ride to the station in the back of a shuttle.
The Endeavour orbiter flight, which will take up the Cupola as a co-passenger, is currently scheduled to lift-off in February 2010.
We are working on the possibility, or at least we are verifying the possibility, of keeping our hardware certified up to 2025
Simonetta Di Pippo
The installation of the two European components will all but complete the construction phase of the International Space Station.
"We still have growth opportunities," said Nasa space station manager Mike Suffredini, who had travelled to Turin to accept the Node on behalf of the US space agency.
"If someone wanted to bring another module to orbit, they could - and our Russian friends do have another couple of modules they are proposing. But the key for us all in the partnership is to concentrate now on utilisation," he told BBC News.
The delivery of Node 3 concludes a barter arrangement made between Europe and the US, in which Europe agreed to supply two connecting nodes, 2 and 3, in return for a free trip into space for its Columbus science laboratory.
NODE 3 - 'TRANQUILITY'
Key unit connects and helps manage other ISS modules
Multiple docking ports for visiting vehicles or future modules
7m by 4.6m; a mass of 14 tonnes, but will be fitted out in orbit
Sophisticated life support systems will include air cleaning unit
Cupola to be fixed to an Earth-facing port once in orbit
Panoramic views provide ideal control room for robotic arm
Named after Sea of Tranquility, the Apollo 11 landing site
The US has already met its side of the bargain, flying Columbus to the station last year.
Some 7m in length and about 4.5m in width, Node 3 is built around the same design principles as Europe's other space station contributions.
Columbus, Node 2, the ATV space freighter, and the Multi-Purpose Logistics Modules (which serve as the packing boxes for major re-supply missions carried out by the US shuttle) all have a similar cylindrical look about them.
Node 3 has several racks inside its multi-layer, meteoroid impact-hardened shell. These bays will quickly become filled in orbit by equipment already on the station.
Chief among these will be the Environmental Control and Life Support Systems (ECLSS).
Their jobs involve scrubbing the air of carbon dioxide to maintain its oxygen concentration; and recycling waste water, including urine, so it can be drunk again and again.
Node 3 will also store a treadmill the crew will need to use regularly to exercise their bodies and maintain bone density.
One of the risks of living in microgravity conditions is that bones tend to lose strength over time.
The cupola, which is already at Kennedy, will be attached to one end of the Node for the flight into orbit; but once in space, it will be moved to a position that better allows the astronauts to use its windows to see across the full breadth of the platform.
The Cupola will afford panoramic views
Although Node 3 is the last major fixed item Europe will send up to the platform, it will continue to build space freighters.
These Automated Transfer Vehicles are part of the European Space Agency's (Esa) ongoing "fees" for being part of the space station "club".
By sending several tonnes of food, water, air, fuel and other equipment to the platform every 18 months so, Esa earns places on the ISS for its astronauts.
The latest ATV, known as Johannes Kepler after the great 17th Century German scientist, has been in preparation here in the same clean-room facility as Node 3.
It is conceivable that the space station partners will order more - or even replacement - fixed modules in the future, but this will depend very much on how long they choose to operate the platform.
Johannes Kepler will also fly in 2010
At the moment, they have no agreement in place to keep flying the station beyond 2015; but Simonetta Di Pippo, Esa's director of human spaceflight, says discussions are likely to resolve this issue soon.
"We are working on the possibility, or at least we are verifying the possibility, of keeping our hardware certified up to 2025," she told BBC News.
"For sure, the first step will be to work on an extension up to 2020."
Node 3 is due to leave Thales Alenia Space on Sunday, to be transported by an Airbus Beluga heavy-lift aircraft to Kennedy.
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