The "Spectroscopy of Plasma Evolution from Astrophysical Radiation" mission

Abstract

The "Spectroscopy of Plasma Evolution from Astrophysical Radiation" ( SPEAR, also known as the "Far-Ultraviolet Imaging Spectrograph") instruments, flown aboard the STSAT-1 satellite mission, have provided the first large-area spectral mapping of the cosmic far-ultraviolet (FUV; 900 - 1750 angstrom) background. We describe the mission and its science motivation, the mission data and their processing, and the effects of mission performance on the science data. We present the first map of the cosmic FUV background (1360 - 1710 angstrom) over most of the sky as an example of the mission results. These SPEAR data reveal diffuse radiation from warm and hot ( 10(4)-10(6) K) plasma, molecular hydrogen fluorescence, and dust-scattered starlight. They allow for an unprecedented characterization of the spectral emission from a variety of environments, including the general interstellar medium (ISM), molecular clouds, supernova remnants, and superbubbles.