After a three and a half year hiatus, construction of the International Space Station (ISS) is finally going to continue. One of the largest pieces, a power generating structure, will be attatched to the ISS. Weighing 17.5 tons, the 240 foot solar arrays on the P3P4 truss segment will generate 20 kilowatts. The 11 day mission could begin as early as August 27. Atlantis' crew members have been training for this mission for four and a half years, since before the Columbia tragedy.WMV video link
The station is nearly halfway through assembly. The next four flights will bring new truss segments, massive structural support beams, to the complex. The new segments will increase the mass of the station by almost 40 tons, the maximum weight of an 18-wheeled semi-truck.
Two of the trusses include huge sets of solar array wings, totaling more than 17,000 square feet. With a wingspan area the size of a national standard hockey rink, the panels will carry 130,000 solar cells. The new segments include giant rotary joints to allow the tips of the station "backbone" to move as the massive panels track the sun. NASA
To construct the station, more than 100 international space flights will have been conducted on five different types of vehicles launched from four different countries. If all goes well the ISS will be completed in 2010.
Read more about the ISS at Wikipedia.