By Jonathan Amos
Cape Canaveral, Florida
Europe hopes finally to get its space station laboratory, Columbus, into orbit this Thursday.
The space shuttle Atlantis will loft Columbus into orbit
The module will be taken up inside the shuttle Atlantis when it launches from the Kennedy Space Center in Florida.
Columbus is intended to be the focal point of Europe's space station activities, which have so far cost five billion euros.
Once the module is in place, astronauts will begin an intensive programme of research in weightless surroundings.
The scientific studies will impact diverse fields, from crop breeding to the development of advanced alloys.
The experiments will also help researchers better understand the physiological demands of long-duration spaceflight, something that will be important if humans are ever to colonise the Moon or travel to Mars.
"Columbus means so much to Europe," said Alan Thirkettle, the European Space Agency's (Esa) space station programme manager.
"It means finally we will have our own real estate on-orbit - a multipurpose research laboratory that gives us the opportunity to do the world-class science we've been looking forward to for such a long time," he told BBC News.
The scheduled launch time on Thursday is 1445 EST (1945 GMT).
Columbus should have flown in December but the 1.3bn euro ($1.8bn; £0.9bn) lab was held on the ground while the US space agency (Nasa) got to grips with a faulty fuel sensor system in the shuttle.
Total length - 6.8m
Diameter - 4.5m
Volume - 75 cu m
Launch mass - 12.8t
Operation - 3 crew
Cabin temp - 16-27C
Total power - 20kW
In a number of recent launch attempts, the engine cut-off, or Eco, sensors have sporadically given out readings indicating orbiter fuel tanks are dry even when they have just been topped off with propellant.
Mission managers decided the issue had to be resolved before Atlantis could lift off; and engineers were ordered to strip back the system and fix what were believed to be poor electrical connections in the wiring between the sensors and the shuttle's computers.
The two-month delay has had no impact on Columbus itself. The module, stored in Atlantis' cargo bay, has been closed up since October.
However, biological samples (Arabidopsis plants) intended for use in some of the first experiments have had to be exchanged for fresh supplies. These specimens, though, are taken up in the mid-deck of the orbiter and are easily changed over.
Leopold Eyharts will stay on the station to commission Columbus
Columbus will be installed on Day Four of the 11-day shuttle mission.
The 7m-long (24ft), 4.5m-wide (14ft), 12.8-tonne laboratory will be manoeuvred into position by the shuttle's robotic arm, and docked to the station's Harmony Node 2 connector.
Hans Schlegel, the German Esa astronaut on the flight, will play a key role in this process, carrying out two spacewalks to get the job done.
First of two
His French Esa colleague, Leopold Eyharts, will be staying on the station to commission Columbus, a process that should take a few weeks to complete fully.
"The scope of the mission is first of course to bring the Columbus laboratory to space, to install it on the international space station, make all the connections, and of course activate the module, power it and bring the cooling and do all the activation," said the Mir space station veteran.
"We will have then to check that all the systems are working properly, the scientific racks are working properly, and [we] will have to do some commissioning tasks - which means checking all the systems.
"And then during the next phase, when the shuttle is gone, my job will be to do some of the experiments on board the module and also to make sure that the scientific racks are working as expected."
Columbus contains a number of science racks. Each is a laboratory in its own right. Experiments in life sciences, physiology and physics can all be carried out within the one structure.
Experimental payloads can also be mounted on the outside of Columbus. On the Atlantis flight, an observatory to study the Sun will be installed, together with a suite of instruments to examine how materials are affected by long exposure to the space environment.
Data from the module will be passed down in real-time through the Columbus control centre, in Oberpfaffenhofen in Germany, to researchers across the globe.
February is set to be one of the most significant months in the history of the 17-member-state European Space Agency. In the next few weeks, it will launch its unmanned logistics ship to the space station.
The Automated Transfer Vehicle is designed to find its own way to the platform. It can haul up to 7.5 tonnes of supplies to the orbiting outpost.