Space Shuttle Endeavour launch held up by space traffic jam

Endeavour is scheduled to launch a day later than previously planned on its visit to the International Space Station, to make room for an unmanned cargo ship.

A looming traffic jam in space has caused NASA to push back the planned launch date for the final voyage of the space shuttle Endeavour by one day.

Endeavour is now slated to lift off toward the International Space Station Feb. 27, 2011 – a day later than previously planned – to allow another spaceship time to arrive at the orbiting laboratory. The fuel tank for Endeavour's last flight arrived at NASA's Kennedy Space Center in Florida last month.

The slight flight delay for Endeavour will clear the way for the European Space Agency to launch an unmanned cargo ship – the Automated Transfer Vehicle-2 – toward the station. That launch, originally planned for December, is now tapped for Feb. 15, with docking at the orbital outpost slated for Feb. 26. Endeavour would then launch the next day and, if all goes as planned, arrive at the station on Feb. 28.

It will be a busy time in space, and that, in part, is because of an earlier bunching of planned flights at the end of this year. ESA officials agreed to push back the ATV-2 launch to February because of delays from the commercial Arianespace company, which builds the Ariane 5 rocket planned to carry ATV-2 to orbit.

The mission is the second flight of Europe's new unmanned space freighter series. The first ATV, Jules Verne, completed a successful cargo-delivery trip to the space station in 2008.

Meanwhile, Russia's Federal Space Agency will continue to ferry cosmonauts and astronauts to the station on Soyuz flights during this time. An Orbital Sciences Taurus Rocket is also scheduled to loft the NASA Glory climate satellite to orbit Feb. 23.

The shuttle Endeavour will be making its last trip to space to deliver a nearly $2 billion cosmic ray particle physics detector to study fundamental physics and cosmology questions. Astronauts will take three spacewalks to install the experiment on the outside of the space station.

Endeavour's STS-134 mission was originally planned to be the final space shuttle flight before the three-orbiter fleet is retired. Last week, though, Congress passed a NASA authorization bill that approved funding for one more shuttle trip – a mission for the shuttle Atlantis that would likely fly in summer 2011.

That bill must be signed into law by President Obama before NASA has official approval for the mission. Experts say the president is likely to sign the bill.

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IN PICTURES: In orbit