Spitzer's spacecraft refers to the uncooled portion of the observatory, including the Solar Panel Assembly, the Spacecraft Bus, and all of 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 two main parts: the solar panels, which provide electrical power to the spacecraft and shield the Cryogenic Telescope Assembly from the Sun; and the spacecraft bus: an octagonal structure that houses the avionics and the warm electronics parts of the science instruments. The spacecraft provides electrical power to the science instruments, orients and stabilizes the telescope, stores and compresses the data from the science instruments for later transmission to Earth, executes the stored commands to carry out the planned observing schedule, and communicates with the ground system. All communications with Spitzer take place through NASA's Deep Space Network.