Original 36-inch reflecting telescope that flew on the Shuttle twice as part of the ASTRO mission. It employs a medium dispersion spectrometer at a modified prime focus. It was designed to observe faint celestial objects in the ultraviolet region of the spectrum. On the first mission in December 1990 the instrument observed over 75 astronomical sources including active galactic nuclei, quasars, variable stars and supernova remnants. After this successful mission it was modified to concentrate on the relatively unknown far-ultraviolet region and flown on Astro-2 in March 1995. Observations from this second flight provided a wealth of data including the first clear detection of the distribution of intergalactic helium left over from the Big Bang. Its calculated distribution in the pre-galaxy formation Universe fits the bubble and void geometry seen in the earliest and present universe. The telescope was manufactured by the Center for Astrophysical Sciences and the Applied Physics Lab of Johns Hopkins University. It was transferred by NASA in 2001.