- Separation of the specroscopic beams from the photometric beams.
- Spectral analysis at three different resolving power values, by the means of selecting either a prism (LR mode, R=30), a medium resolution grism (MR mode, R=1500), or a high resolution grism (HR mode, R=12000).
- Formation of the images on the detector plane.
All these functions are accomplished in the spectral range which covers the astronomical red / near-infrared bands J, H, and, K(i.e. 1.05 to 2.4 µm). The optics and the support structure are contained in a vacuum tight cryostat which allows the cooling of thewhole spectrograph to the working temperature of about 77K by means of liquid nitrogen at atmospheric pressure.
An in-depth description with designs and drawings of the AMBER Spectrograph (SPG) can be found at: AMBERSPG web-site at ARCETRI.