TMT’s primary segmented mirror will be made up of 492 smaller mirrors and measure thirty meters across—three times the diameter and nine times the collecting area of the giant Keck Telescope. Once considered inferior to space-based telescopes like Hubble, ground-based optical telescopes are rapidly overtaking their space-based brethren. TMT will deliver images 12 times sharper than those taken by Hubble.
How’s that possible? The first ground-based strategy is to locate in a remote place to minimize pollution (light and air) and high up to minimize cloud cover. Hawaii’s Mauna Kea is an ideal spot, and its slopes are already dotted with observatories.
But the atmosphere itself, no matter how clear or free of pollution, deforms light waves. Computer-powered adaptive optics correct that distortion by studying a laser-projected artificial “guide star” near the point of observation in the upper reaches of Earth’s atmosphere. The telescope’s computer notes how the layers of air distort the guide star’s light and uses actuators to shift segments of the primary mirror, correcting the observed wave pattern.