(I) IRAS was one of the most productive satellites in the history of astronomy. (II) Though functional for only 10 months in 1983, the observations it performed continue to be a major source of information for astronomers. (III) The satellite undertook a complete survey of the sky in mid- and far-infrared light, with wavelengths between 12 and 100 microns. (IV) The spectrum also reveals the geometry of the dust. (V) This part of the spectrum is difficult or impossible to detect from the ground so the survey was of immense importance.