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The Hopkins Ultraviolet Telescope: Performance and Calibration during the Astro-1 Mission

Arthur F. Davidsen, Knox S. Long, Samuel T. Durrance, William P. Blair, Charles W. Bowers, Steven J. Conard, Paul D. Feldman, Henry C. Ferguson, Glen H. Fountain, Randy A. Kimble, Gerard A. Kriss, H. Warren Moos, and Kenneth A. Potocki


The Hopkins Ultraviolet Telescope (HUT) was flown aboard the space shuttle Columbia on the Astro-1 mission from 1990 December 2--11. Spectrophotometric observations of 77 astronomical sources were made throughout the far ultraviolet (912--1850 Å) at a resolution of 3 Å, and, for a small number of sources, in the extreme ultraviolet (415--912 Å) beyond the Lyman limit at a resolution of 1.5 Å. The objects observed include quasars, galaxy clusters, active and normal galaxies, cataclysmic variables, globular clusters, supernova remnants, planetary nebulae, white dwarfs, Wolf-Rayet stars, Be stars, cool stars with active coronae, comet Levy (1990 XX), Jupiter and Io. HUT has provided the first spectrophotometry in the sub-Lyman- region for most of these sources. In this paper we describe the HUT instrument and its performance in orbit. We also present a HUT observation of the DA white dwarf G191-B2B and derive the photometric calibration curve for the instrument from a comparison of the observation with a model stellar atmosphere. The sensitivity reaches a maximum at 1050 Å, where 1 photon cm s Å yields 9.5 counts s Å, and remains within a factor 2 of this value from 912 to 1600 Å. The instrumental dark count measured on orbit was less than counts s Å.