STS048-09-019 (16 Sept 1991) --- Astronauts Mark N. Brown, left, and James F. Buchli work with the structural test article (STA), a model of the space station truss structure. STA is part of the middeck zero gravity dynamics experiment (MODE). MODE was designed to study the vibration characteristics of the jointed truss structure. The structural test article includes four strain gauges and eleven accelerometers and is vibrated by an actuator. Assembled by crewmembers in the Shuttle orbiter's middeck, the device is about 72 inches long with an 8-inch square cross section.