Arved Sapar observed the spectra of the stars and the interstellar matter in the ultraviolet radiation with the NASA satellite-telescope IUE (International Ultraviolet Explorer).

Among the Estonian astronomers Arved Sapar is the only person who has granted observation time of the NASA satellite-telescopes. The result of this observation is to register the spectra of the substances of many massive early type stars and the interstellar matter. With the help of the spectra the detailed composition of the atmospheres of hot stars and the movement of the matter in them was studied.

International Ultraviolet Explorer (IUE) ground station