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Extrapolations of the cost and weight of the present Hubble Space Telescope to larger diameters lead to telescopes which are very heavy and expensive. We plan to build a prototype of a diffraction limited, large space telescope and fly the prototype on a tethered aerostat in Antarctica. During the austral winter the cold, stable, dry, high altitude environment over the Antarctic plateau provides a relatively inexpensive way to test prototypes of space instrumentation. A standard 71 m aerostat can lift a 2000 to 4000 lb payload to a height of 6 km above the 3 km high Antarctic plateau, depending on the weight of the tether. The tether can carry 20 kwatts of power to the telescope and aerostat, and can transmit data at high rates through a fiber. As an intermediate step, we plan to fly a passively cooled 2.4-m IR telescope. At a pressure of 300mb, the overburden of Antarctic water vapor is expected to be under 10 microns of precipitable water. Very long duration exposures in a low background environment will permit the balloon telescope to image fainter objects than any instrument on the Earth or presently in Space. We intend to use the IR and optical telescopes for optical and near IR high angular resolution imaging of the centers of active galaxies, high redshift galaxies, and circumstellar disks and brown dwarfs around nearby stars. Our present concept for the final optical telescope is a sparsely filled array of six 80-cm mirrors on a 6-m diameter circle. Each mirror will be a segment of an f/1 RC primary. The mirrors will have an unequal spacing around the circumference which optimizes spatial coverage of the UV plane.
The tethered aerostat will provide a high altitude polar platform which will be invaluable for optical, IR and sub-mm, solar, meterological, and atmospheric chemistry observations.
