Keck Observatory — From a remote outpost on the summit of Hawaii’s dormant Mauna Kea volcano, astronomers at the W.M. Keck Observatory probe the deepest regions of the Universe with unprecedented power and precision.
Their instruments are the twin Keck Telescopes, the world’s largest optical and and infrared telescopes. Each stands eight stories tall and weighs 300 tons, yet operates with nanometer precision.
At the heart of each Keck Telescope is a revolutionary primary mirror. Ten meters in diameter, the mirror is composed of 36 hexagonal segments that work in concert as a single piece of reflective glass.
Made possible through grants totalling more than $140 million from the W.M. Keck Foundation, the observatory is operated by the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA), which joined the partnership in October, 1996. The Keck I telescope began science observations in May, 1993; Keck II began in October, 1996.
Keck’s capabilities make full use of the summit site. Surrounded by thousands of miles of relatively thermally-stable ocean, the 13,800 foot Mauna Kea summit has no nearby mountain ranges to roil the upper atmosphere or throw light- reflecting dust into the air. Few city lights pollute the viewing. For most of the year, the atmosphere above Mauna Kea is clear, calm and dry.
An altitude-azimuth design gives each Keck telescopes the optimal balance of mass and strength. Extensive computer analysis has given them the greatest strength and stiffness for the least amount of steel – about 270 tons per telescope. This is critically important, and not only for economic reasons. A large telescope must remain resistant to the deforming forces of gravity as it tracks objects moving across the night sky.
Chilling the interior of the insulated dome during the day controls temperature variations that could induce deformation of the telescope’s steel and mirrors. This is a big task; each dome contains more than 700,000 cubic feet of volume. Giant air conditioners run constantly during the day, keeping the dome temperature at or below freezing. At night when the dome is opened, exposing the telescopeto the frigid night air, the telescope already is at the ambient outdoor temperature.
Astronomers use the telescopes in shifts of 1-4 nights. Time-allocation comittees pre-approve all observing plans. Observing assistants operate the telescopes while astronomers gather data from the science instruments.