NASA says excessive vibration caused by repositioning the International Space Station last month may have shortened the useful life of the $100 billion orbiting lab. A faulty rocket command sequence aboard the international space station caused the 300-ton structure to shake back and forth vigorously for two minutes last month, during what was supposed to be a routine, gentle orbital adjustment.

Rockets used to change the station's location cut off abruptly rather than gradually, causing the station to shake more than it usually does.

Flight engineers do not like moving the ISS using rocket thrusters, and normally only move the multi-billion space station when a piece of debris may impact it, NASA officials said. Russian engineers last month sought to position the station to receive a robotic spacecraft on February 13.

The rockets used to change the station's location cut off abruptly rather than gradually, said NASA spokesman Kelly Humphries said.

Partly as a result of last month's anomaly, a second rocket burn originally scheduled for Wednesday has been canceled.
NASA plans to launch shuttle Discovery to the ISS to deliver the last solar arrays on February 12, with five total shuttle missions planned for 2009.  The U.S. space agency desperately wants to have the ISS fully operational, but does not plan to use the orbiting space lab after 2015.  The 13 other nations who helped construct the ISS want to continue using it until 2020.

Delays in construction mean that the station, which was started in 1998, still isn't finished and has been occupied by skeleton crews of two or three people. The first full crew of six people is scheduled to take up residence in May.