The Arcetri Infrared Instrumental Group is involved in design, building and testing the Spectrograph (SPG) of the instrument.
The cold spectroraph of AMBER (indicated by the acronym SPG in AMBER documentation), besides operating the spectral dispersion of incoming beams, includes the following functions:

• Formation of an image of the fiber outputs at cryogenic temperature and filtering of thermal radiation from this image by means of suitable spatial filters
• Formation of a parallel beam
• Accurate spatial filtering of the pupils
• Separation of specroscopic beams from photometric beams
• Spectral analysis at three resolving power values
• Formation of images on the detector plane

All this functions are accomplished in the spectral range which covers the astronomical near-infrared bands J, H, K, that is 1.0 to 2.4 µm. The optics and the support structure are contained in a vacuum tight cryostat which allows the cooling of all functions to the working temperature of about 77 K by means of liquid nitrogen at atmospheric pressure.