The Cryogenic Telescope Assembly
All of Spitzer's cold items are kept in the Cryogenic Telescope Assembly (CTA), which is made up of four main-parts: The Telescope, Multiple Instrument Chamber (Infrared Array Camera, Infrared Spectrograph, and Multiband Imaging Photometer), Cryostat, and Outer Shell Group.
A tank of liquid helium, called the "cryostat", acts as a coolant - producing a freezing vapor that cools the entire CTA to about five degrees Kelvin (-459 Fahrenheit, or -268 Celsius).
To prevent the liquid helium from being used up too quickly, the CTA is attached to the telescope with special insulating struts, and is surrounded by a series of thermal radiation shields that prevent heat from the spacecraft from reaching the telescope.
The outer shell of the Observatory is made of aluminum. It is painted black on the side facing away from the Sun, to radiate as much heat into space as possible, and is shiny on the Sun-facing side, to reflect the Sun's light instead of absorbing it. The solar array and the spacecraft shields block the CTA from the Sun and the rest of the spacecraft at all times, helping to keep the CTA as cool as possible.