NASA announced that it extended the Atlantis STS-122 space mission to allow for the European space lab Columbus to be fully checked after its installation on the International Space Station. This means that Atlantis and its crew is now scheduled to land at the Kennedy Space Center in Florida on Wednesday at 1406 GMT, NASA said. The shuttle will leave the ISS on Monday.

Yesterday, German Chancellor Angela Merkel called the ISS to talk to the two European astronauts Hans Schlegel and Léopold Eyharts. She was joined at the public event which took place at the Federal Ministry of Economics and Technology in Berlin by ESA Director General Jean-Jacques Dordain, Prof. Jan Wörner, Chairman of the Board of DLR, Federal Minister Michael Glos and Evert Dudok, CEO of Astrium Satellites.

"We are proud as Germans and Europeans that we could contribute to the ISS with Columbus. Europe now has a permanent basis for research in space," she said.

For today, the final spacewalk is scheduled by US astronauts Rex Walheim and Stanley Love. The two had to spend their night in the station's decompression chamber to prepare themselves for the six hour and 35 minute spacewalk which is set to begin at 1340 GMT. They are to install an observatory to monitor the sun, among other activities.

"We can get a more accurate reading in space than we could on Earth with the same instruments," Bruno Musetti, the chief engineer for the project, told the Reuters news agency.

Also, Rex Walheim and Stanley Love will have to retrieve an old space station gyroscope and examine the jammed solar rotary joint which was previously found to have metal shavings in it due to metal on metal friction. There is also another problem, a tiny chip on a handrail near the spacewalk hatch which is believed to be caused by a micrometeorite strike. The problem is that the chip has apparently caused the astronauts' gloves to tear.

Yesterday, ESA astronaut Hans Schlegel, who was earlier affected by health problems, and his colleague NASA astronaut Rex Walheim have completed the second spacewalk of the STS-122 Shuttle mission which lasted six hours 45 minutes. They worked on replacing a nitrogen tank used to pressurize the Station's ammonia cooling system.

The $2 billion lab will allow experiments to be conducted on the behavior of weightless liquids, and on micro-organisms, cells and tissues.

Columbus is designed for ten years of operation and will be controlled by the special Columbus Control Centre, located at the German Space Operations Centre, part of the German Aerospace Center (DLR). On May 27 last year, the Columbus lab was flown from Bremen to Kennedy Space Center on board an Airbus Beluga.