The SPAS (Shuttle Pallet Satellite) is a battery powered, 3-axis stabilized spacecraft which provides mechanical interface, power, command, low rate telemetry and high density data storage. A reconfigured SPAS for the SPAS III mission has been defined which includes new avionics and power subsystems, a modified communications subsystem, a Global Positioning System receiver, and a new sensor suite. The primary sensors are an IR (Infrared) Radiometer, an IR Spectrometer, a Multi-Spectral Imager/Spectrometer and two television cameras. The SPAS is deployed from the STS (Space Transportation System) orbiter for approximately four days, controlled with either ground or Astronaut commands, and then retrieved.
Due to its externally mounted sensors and components, and widely varying possible orbital attitudes and mission conditions, the SPAS presented a challenging thermal design opportunity. This paper describes the design approach, problems encountered in the design process, and final thermal design. The thermal modeling of the SPAS is discussed. Flight temperature predictions are also included for both STS attached and free flyer mission phases.