A balloon-borne three-meter telescope for far-infrared and submillimeter astronomy has been proposed jointly by the University of Arizona, the Smithsonian Astrophysical Observatory, and the University of Chicago. The purpose of this project is to provide a facility for photometry, spectroscopy, and imaging in the spectral region 30 micrometers to 1 millimeter, which is largely inaccessible with ground-based telescopes. The three-meter telescope will provide a much needed gain in sensitivity and spatial resolution compared with present approximately one-meter sized balloon and aircraft telescopes. The telescope is to be a Cassegrain design with an angular resolution diffraction limited to a wavelength of 30 microns. It will be supported on a three axis, gyroscopically-stabilized system with a pointing stability of one arcsecond rms. The overall weight of telescope and gondola is expected to be approximately 2800 kg, assuming a lightweight mirror formed as a welded structure of Pyrex or fused silica. We are also studying the possibility of using a carbon fiber reinforced plastic sandwich panel for the primary and secondary mirrors and carbon fiber reinforced plastic members for the telescope structure. The intended operation is approximately five 8 to 10 hour flights per year carrying two instruments at a time.
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