Discovery's seven astronauts conducted a very meticulous and difficult inspection of the space shuttle Wednesday, focusing on three wing panels to make sure possible cracks spotted beneath the shuttle's protective coating had not worsened.

The inspection occurred on the 1st full day of what NASA considers to be the most complicated international space station construction mission yet. The shuttle was to reach the station Thursday.

Commander Pamela Melroy and her crew used a laser and camera-tipped inspection boom to check Discovery's wings and nose.

However, the astronauts went a little more slowly to capture more detailed images of three of 44 wing panels where it is possible there are cracks beneath the coating.