A multipayload spacecraft modeling approach that combines constituent
subassemblies (plant and controllers) into a combined system (model sy
nthesis) is presented. This technique was used to model the Upper Atmo
sphere Research Satellite. The simulation was developed to determine t
he amount of controls-structure interaction, and the satellite flight
results verified simulation predictions during payload tracking and sc
an modes and solar-array sun-tracking modes, The simulation was develo
ped using the Dynamics Analysis Design System program, The program was
modified to include a multirate sampling capability, a robust analog
delay element, a stepper-motor kinematic driver, and a modified flexib
le body formulation. The simulation includes the structural models of
the satellite components, the dominant flexible modes, the vehicle att
itude control system and orbit adjust capability, and all instrument e
levation and azimuth control systems. The model includes the flexible
modes below 16 Hz and the instrument control systems. This study prese
nted simulation results using the synthesized modeling approach and th
e in-flight data to validate the approach