FUSE is the Far Ultraviolet Spectroscopic Explorer.
It is a telescope that is in orbit, and it's designed specifically to do spectroscopy at very short far-ultraviolet wavelengths.
It is a unique facility because it can look at wavelengths way beyond what can be done with the Hubble Telescope.
It is a very specialized area of the spectrum, but it is also the richest part of the spectrum.
In this part, from 900 to 1200 angstrom wavelengths, you see the lines from the hottest and most common elements that we know about – particularly the line series of hydrogen – and there are literally hundreds of lines from the interstellar medium.
So, it is a very powerful region of the spectrum and this is a telescope that enables us to study it in all its richness.