FIGURE 7.9 The two U.S. Giant Segmented Mirror Telescope projects. Upper: The Giant Magellan Telescope is a 25-meter-class telescope comprising seven 8.4-meter subapertures, one of which is already undergoing polishing. Laser tomography will provide adaptive optics correction in small fields over much of the sky, and correction for ground-level seeing will be incorporated over large fields. The baseline project includes an initial suite of three to four instruments to be selected in 2011 from eight concepts currently in development. Artist’s rendering of GMT and support facilities at Las Campanas, Chile. SOURCE: Courtesy of GMTO; image by Todd Mason/Mason Productions. Lower: The Thirty Meter Telescope primary mirror comprises 492 hexagonal segments with active control and a 30-meter-effective-diameter aperture. An on-axis segment has been cast and polished, and an off-axis segment is currently undergoing polishing. Nine instruments are planned for the first decade of operations, of which three are planned for first light. Most of these instruments operate in conjunction with sophisticated adaptive optics systems. SOURCE: TMT Observatory Corporation.