Each of the three scanning telescopes, shown on the right stacked in pyramid fashion, is the size of a 55-gallon oil drum and each weighs about 116 kg (256 lb). By using specially designed, very thin, filters placed in front of each detector, these telescopes produce sky maps in four different extreme ultraviolet spectral bands. The all-sky survey phase of the EUVE mission required 6 months of observations with the scanning telescopes. From these data, Berkeley scientists have produced a comprehensive sky map and catalog of the positions and intensities of extreme ultraviolet sources.
Two of the scanning telescopes are nearly identical, to check observations and to ensure a backup capability in the event of a malfunction. They are used for observing at the high-energy, short-wavelength end of the extreme ultraviolet spectral band (70 to 400 Angstroms) -- the energy range within which most sources have been detected (left, top). These telescopes have gold-plated mirrors, with very small grazing angles to reflect the maximum amount of radiation at these higher energies. The third scanner (left, bottom) is specially designed to observe at the low-energy, long wavelength end of the extreme ultraviolet spectral band (400 to 760 Angstroms). Its mirrors are plates with a special nickel alloy and use larger grazing angles to reflect the maximum amount of lower energy radiation.