(03/12/2002) -- Its immense size dwarfing the van driving in front of it, Space Shuttle Atlantis inches toward the launch pad. Both the Rotating Service Structure (open) and the Fixed Service Structure, which holds the 80-foot lightning mast on top, are seen at right. The Shuttle sits on top of the Mobile Launcher Platform, which rests on the crawler-transporter. Atlantis is scheduled for launch April 4 on mission STS-110, which will install the S0 truss, the framework that eventually will hold the power and cooling systems needed for future international research laboratories on the International Space Station. The Canadarm2 robotic arm will be used exclusively to hoist the 13-ton truss from the payload bay to the Station. The S0 truss will be the first major U.S. component launched to the Station since the addition of the Quest airlock in July 2001. The four spacewalks planned for the construction will all originate from the airlock. The mission will be Atlantis' 25th trip to space