Atop the massive mobile launcher platform and crawler-transporter Space Shuttle Atlantis creeps toward Launch Pad 39A.

Atop the massive mobile launcher platform and crawler-transporter, Space Shuttle Atlantis creeps toward Launch Pad 39A, seen in the background. First motion was at 8:19 a.m. The 3.4-mile trip along the crawlerway will take about 6 hours. The mission payload aboard Space Shuttle Atlantis is the S3/S4 integrated truss structure, along with a third set of solar arrays and batteries. The crew of six astronauts will install the truss to continue assembly of the International Space Station. Launch is targeted for March 15. Photo credit: NASA/Kim Shiflett