The Giant Magellan Telescope (GMT) Mirror cells provide positioning, support, with active optics compensation, and thermal control of the seven 8.4 meter primary mirror segments. Each mirror cell is a large steel welded structure, and in the case of the outer off axis segments, is designed to be interchangeable for any one of the 6 possible mirror positions. The mirror support and active optics compensation are provided through a series of single axis and three axis pneumatic actuators that control the force used to support the mirror at a total of 165 positions and allows for support of the mirror in any one of the six positions. Mirror positioning is provided by a stiff hexapod actuator system between the mirror and the mirror cell. Mirror thermal control is provided by a series of fans that pressurize the mirror cell and condition the air before it is directed into the mirror through 1700 nozzles.
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