This paper describes the procedure for determination of the weight and the location of the center of gravity (c.g.) of a Space Shuttle Orbiter Spacecraft, at the Kennedy Space Center (KSC), Florida. This task is performed at the completion of the horizontal processing of each Orbiter (Orb) in conjunction with jack down and preparation for vertical mating to the Shuttle launch vehicle. The operation is performed in the Orbiter Processing Facility (OPF). It is conducted by NASA and Rockwell International Corporation personnel of KSC along with Mass Properties Engineers fron theOrbiter design centers of the Johnson Space Center (JSC), Houston, Texas, and Rockwell International Space Division, Downey, California. The following sections will briefly describe the general characteristics and physical dimensions of the Orbiter spacecraft, the program requirements and test procedure for weight and c.g. determination,data evaluation and a summary. In addition, a glossary appears on page 13.