The 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 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.

The Keck Observatory atop Mauna Kea

Made possible through grants totaling more than $140 million from the W. M. Keck Foundation, the Observatory is operated by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California. In 1996, the National Aeronautics and Space Administration (NASA) joined as a partner in the Observatory. The Keck I telescope began science observations in May 1993; Keck II began in October 1996.

Keck's capabilities make full use of Mauna Kea's research potential. Surrounded by thousands of miles of relatively thermally stable ocean, the 13,796-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 its extremely dark skies. For most of the year, the atmosphere above Mauna Kea is clear, calm and dry.

Telescopes

An altitude-azimuth design gives each 10-meter Keck telescope the optimal balance of mass and strength. Extensive computer analysis determined 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: The volume of each dome is more than 700,000 cubic feet. Giant air conditioners run constantly during the day, keeping the dome temperature at or below freezing.

Astronomers use the telescopes in shifts of one to five nights. Time allocation committees pre-approve all observing. Assistants operate the telescopes at the summit while astronomers gather data via remote observing from observatory headquarters in Waimea. The W. M. Keck Observatory was the first facility on Mauna Kea to use remote observing.

The Mirror

A telescope tracks objects, sometimes for hours, across the sky as the Earth turns. This constant but subtle movement results in slight deformations of the telescope structure despite all engineered precautions. Without active, computer-controlled correction of the primary mirror, scientific observations would be impossible.

New techniques for manufacturing, polishing, and testing the mirror segments had to be invented, including "stressed mirror" polishing. Each segment's surface is so smooth that if it were the width of Earth, imperfections would be only three feet high.

On the telescope, each segment's figure is kept stable by a system of extremely rigid support structures and adjustable warping harnesses. During observing, a computer-controlled system of sensors and actuators adjusts the position of each segment - relative to its neighbors - to an accuracy of four nanometers, about the size of a few molecules, or about 25,000 times thinner than a human hair. This twice-per-second adjustment effectively counters the tug of gravity.

Ever since their invention nearly 400 years ago, Earth-based telescopes have suffered from image blurring caused by the turbulent atmosphere above them. This is true of even the world's best observatory sites like Mauna Kea, though to a considerably lesser extent than elsewhere. In recent years, advances in optical and computing technology have made it possible to greatly reduce this blurring through the use of "adaptive optics" (AO). At the heart of the AO system is a 6" diameter deformable mirror that changes its shape up to 670 times per second to cancel out atmospheric distortion, resulting in images 10 times sharper than before. The successful installation of AO systems on both Keck telescopes has made it possible for Keck astronomers to study objects in far greater detail than ever before.

Research

Today, the Keck telescopes are used to seek answers to ancient questions: How did the universe evolve since creation to its present state? How, and when, did galaxies form? What is the rate of star formation in galaxies far away, and far back in time? How much does the expansion rate of the universe vary over history? How do solar systems form? Where is the missing mass of the universe? What is the ultimate fate of the universe? In just the past few years, astronomers at the W. M. Keck Observatory have made tremendous progress in answering these and other questions. Among numerous research projects, Keck astronomers are using gravitational lenses to discover galaxies at the edge of the universe; using supernovaes to determine the expansion rate of the universe; searching for atomic gases in the immense regions of space between galaxies; helping to solve the riddle of gamma ray bursts, and discovering planets around other stars.

The next phase of the W. M. Keck Observatory is underway as teams of scientists and engineers continue work on improving the Keck Interferometer. The Keck-Keck Interferometer combines the light of both Keck telescopes to obtain a tenfold increase in resolution. It is a significant cornerstone of NASA�s "Origins" program, which ultimately seeks to identify and characterize planets around Sun-like stars. The interferometer will also help astronomers detect giant gas planets, measure and characterize planet-forming dust around stars, and obtain extremely high-resolution images of protoplanetary disks. It has already produced significant results, including observation of a supermassive black hole in the center of a galaxy (NGC 4151) more than 40 million light years away.

An altitude-azimuth design gives each 10-meter Keck telescope the optimal balance of mass and strength. Extensive computer analysis determined the greatest strength andstiffness 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.

Headquarters

The Observatory Headquarters is an architecture-award-winning facility located on a 7-acre campus in Kamuela on the Big Island of Hawaii. The land for our headquarters was donated by Parker Ranch.

Named by the 2000 Robb Report as one of the 10 most desirable places to live in the country, Kamuela is a charming town of 6,000; it sits 2,500 feet above sea level and offers a peaceful, rural lifestyle, a benign climate, excellent schools, and freedom from the frenetic pace so characteristic of much of the mainland United States.

About 125 people work full-time at Keck, of which two-thirds were hired from Hawaii. With an annual operating budget of $11 million, the Observatory is one of the town's largest employers.

Instrumentation