Abstract
The ESO's Very Large Telescope will employ an array of four 8-m aperture telescopes which can be operated in either independent or combined modes, as well as in an interferometric mode. The primary mirrors used are of thin, Zerodur glass-ceramic meniscus type, figured for f/1.8; the overall design is optimized for f/15 at the Nasmyth foci. Active optics are employed to compensate for slowly varying deformation and thermal distortion effects, as well as wind buffeting. Wavefront sensing for active figure maintenance is accomplished by means of a Shack-Hartmann CCD wavefront sensor which is integrated with the imaging CCD used for field acquisition and tracking. Two types of enclosure are under consideration for the telescope which attempt to maximize natural ventilating flows.

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