Keck II Telescope interior.
The Keck Telescopes are two of the largest optical and infrared telescopes currently in use. Located at the Keck Observatory in Hawaii, both have primary mirrors 10 meters (33 feet) in diameter, made from 36 1.8-meter-wide hexagonal segments. A computer-controlled system of sensors and actuators adjusts the position of each segment relative to its neighbors, twice a second, to an accuracy of 4 nanometers. Each telescope has 4 times the light-gathering power of the famous 5-meter Hale Telescope and 17 times that of the Hubble Space Telescope.
Keck I began scientific observations in May 1993 and Keck II in October 1996. Attached to Keck I is HIRES, the High Resolution Échelle Spectrometer, used in the search for exoplanets. Among the instruments fitted to Keck II is MIRLIN, the Mid-InfraRed Large-well Imager, capable of showing detail in circumstellar disks and thereby shedding light on the process of planet formation.
The Keck Interferometer was a system in operation from 2003 to 2012 which allowed the light entering the twin Keck Telescopes to be passed through a system of adaptive optics to correct for turbulence in Earth's atmosphere, and combined through optical interferometry. The result of this technology was be to create an instrument with the resolving power of a single mirror 85 meters in diameter. The Keck Interferometer was used for a range of science programs, including studies of active galactic nuclei and the formation of stars and planets.