|Discovery arrived at launch pad after a trip from vehicle assembly building at Kennedy Space Center in Cape Canaveral, Florida|
Wednesday's move to the launch pad was the second in a month for Discovery, which will be the first U.S. space shuttle launch since the 2003 Columbia disaster.
In May, Discovery was sent back to the assembly building over concerns that ice could build-up on its fuel tank, possibly breaking off and causing damage to the ship.
NASA scientists also needed to test sensors on Discovery's fuel tank.
Officials say two sensors that failed during a previous test now work perfectly.
Some information for this report provided by AP and Reuters.