The Truss the cornerstone truss of the Space Station is shown on the floor of the Space Station Processing Facility.

The Zenith-1 (Z-1) Truss, the cornerstone truss of the Space Station, is shown on the floor of the Space Station Processing Facility. The Z-1 Truss was officially turned over to NASA from The Boeing Co. on July 31. It is scheduled to fly in Space Shuttle Discovery's payload pay on STS-92 targeted for launch Oct. 5, 2000. The Z-1 is considered a cornerstone truss because it carries critical components of the Station's attitude, communications, thermal and power control systems as well as four control moment gyros, high and low gain antenna systems, and two plasma contactor units used to disperse electrical charge build-ups. The Z-1 truss and a Pressurized Mating Adapter (PMA-3), also flying to the Station on the same mission, will be the first major U.S. elements flown to the ISS aboard the Shuttle since the launch of the Unity element in December 1998