Credit: TMT International Observatory/Harris/F. Kamphues
Thirty Meter Telescope Primary Mirror Segment. The TMT primary mirror includes 492 hexagonal segments, each about 1.44 meters (56.6 inches) across corners. The segments are closely spaced, with gaps between the segments only 2.5 mm (0.1 inch) wide. The segments will be made from Ohara Clearceram zero expansion glass ceramic. The glass will be 45 mm thick (about 2 inches). Each segment has a support system that holds it in position without distortion from gravity. Twenty-seven thin flexures are attached to the back of the mirror and the weight of the segment is reacted by a whiffletree lever system that spreads the load in the correct proportions to avoid distorting the shape of the segment. The lateral support (required when the telescope points towards the horizon) is provided by a central metallic diaphragm recessed into the glass.
