Infrared Array Camera

[1] It was composed of four detectors that operated simultaneously at different wavelengths; all four were in use until 2009 May 15 when the Spitzer cryostat ran out of liquid helium.

[1][3][5] The telescope's primary and secondary mirrors, along with its supporting structure, were made mostly of beryllium.

[8] The cryogenic assembly of IRAC is contained in the Multiple Instrument Chamber (MIC), which also houses the other focal plane elements and the pointing calibration reference sensor.

[9] The MIC is attached to the cryostat and was intended to keep the science instruments, including IRAC, cold but also functioned to keep out stray light.

[9] The MIC is mounted to the helium chamber inside the cryostat vacuum shell, not only to efficiently keep the instruments cold but to seal out any stray light.

Infrared observations can see objects hidden in visible light, such as HUDF-JD2 shown. This shows how the Spitzer IRAC camera was able see beyond the wavelengths of Hubble's instruments
Four-band IRAC image of the Trifid Nebula . The wavelengths the camera sees are mapped to the visible spectrum for a false color image that humans can see. Here, the mapping is blue for 3.6 μm , green for 4.5 μm, orange for 5.8 μm, and red for 8.0 μm.
IRAC filters