Spitzer's spacecraft refers to the warm portion of the Observatory, including the Solar Panel Assembly, the Spacecraft Bus, and the components mounted in the bus that provide the Observatory engineering functions. These components include: the solar arrays, the command and data handling unit, the reaction control subsystem, the telecommunications subsystem, the power generation and distribution subsystem, the pointing control subsystem, and the flight software.
The spacecraft consists of an octagonal bus structure in which the avionics and the science instrument's warm electronics are housed, and a solar panel that provides electrical power to the vehicle and serves to shade the cryo-telescope assembly from direct exposure to the sun. The spacecraft provides electrical power to the science instruments, orients and stabilizes the boresight of the telescope, collects and compressed data from the science instruments for later transmission to the ground, executes stored commands to direct science instrument activities, and communicates with the ground system. All communications with Spitzer will be conducted through NASA's Deep Space Network. The spacecraft is responsible for the safe operation of the Observatory.