PCR a worker makes sure the Integrated Truss Structure Z1 is ready to be moved into the payload bay of Space Shuttle Discovery.

Inside the Payload Changeout Room (PCR), a worker makes sure the Integrated Truss Structure Z1 is ready to be moved into the payload bay of Space Shuttle Discovery. The Z1 truss is the first of 10 that will become the backbone of the International Space Station, eventually stretching the length of a football field. Along with its companion payload, the third Pressurized Mating Adapter, the Z1 is scheduled to be launched aboard Discovery Oct. 5 at 9:38 p.m. EDT