Far–IR spectroscopy towards Sagittarius B2

The far–IR is a unique wavelength range for Astrophysical studies, however, it can only be fully sampled from space platforms. The fundamental rotational transitions of light molecules, the high–J transitions of polyatomic species, the bending modes of non-polar molecules, several atomic fine structure lines and many frequencies blocked by the earth atmosphere can only be observed between 50 and 200 μm (6.0 and 1.5 THz). In this contribution we present the far–IR spectrum of Sgr B2 at a resolution of ∼35 km s, the “Rosetta stone” of ISO’s spectra. We also discuss the perspectives of the far–IR Astronomy in the context of the future telescopes under development.