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The telescope design is a three-mirror anastigmat, with the primary mirror reaching a diameter size of 8.4 meters (6.5 meter effective radius). All three mirrors will be actively supported to control wavefront distortions introduced by gravity and environmental stresses on the telescope. The dome that contains the telescope has been designed to reduce dome seeing and to maintain a uniform thermal environment over the course of the night.  The LSST camera contains a 3.2-gigapixel focal plane array comprised of 189 4096x4096 CCD sensors with 10 μm pixels. The focal plane is 0.64 m in diameter, and covers 9.6 {deg^2} {deg$^2$}  field-of-view with a plate scale of 0.2 pixel^{−1}. pixel$^{−1}$.  The CCD sensors are deep depletion, back-illuminated devices with a highly segmented architecture, 16 channels each, that enable the entire array to be read out in two seconds. The detectors are grouped into 3x3 arrays, all identical and each containing its own dedicated front-end and back-end electronics boards, which fit within the footprint of its sensors, thus serving as a 144-Megapixel camera on its own. The CCDs will be maintained at an operating temperature of −100^°C. The grid also contains two guide sensors and a wavefront sensor positioned at each of the four corners at the edge of the field. The entrance window to the cryostat is the third of three refractive lenses. The camera body also contains a mechanical shutter and a filter exchange system holding five large optical filters, any of which can be inserted into the camera field of view for a given exposure. The system will in fact have six filters; the sixth filter can replace any of the five via an automated procedure accomplished during daylight hours. The LSST filter choice (u, g, r, i, z, y) is modeled on the system used for the SDSS, which covers the available wavelength range with roughly logarithmic spacing while avoiding the strongest telluric emission features and sampling the Balmer break. \textbf{Extension of the SDSS system to longer wavelengths (y-band) is possible because the deep-depletion CCDs have}  \textbf{high sensitivity to 1 μm.} Four special purpose rafts, mounted at the corners of the science array, contain wavefront sensors and guide sensors. \textbf{Wavefront measurements are accomplished using curvature sensing,}  \textbf{in which the spatial intensity distribution of stars is measured at equal distances on either side}