Press Release

Laser Points to the Future at Palomar

By SpaceRef Editor
November 6, 2004
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PALOMAR MOUNTAIN, Calif. — The Hale Telescope on Palomar Mountain
has been gathering light from the depths of the universe for 55
years. It finally sent some back early last week as a team of
astronomers from the California Institute of Technology, the Jet
Propulsion Laboratory and the University of Chicago created an
artificial star by propagating a 4-watt laser beam out from the Hale
Telescope and up into the night sky.

The laser was propagated as the first step in a program to expand the
fraction of sky available to the technique known as adaptive optics.
Adaptive optics allows astronomers to correct for the fuzzy images
produced by earth’s moving atmosphere, giving them a view that often
surpasses those of smaller telescopes based in space.

"We have been steadily improving adaptive optics using bright natural
guide stars at Palomar. As a result, the system routinely corrects
for atmospheric distortions. Now we will be able to go to the next
step," says Richard Dekany, associate director for development at
Caltech Optical Observatories. Currently astronomers at Palomar can
use the adaptive-optics technique only if a moderately bright star is
sufficiently close to their object of interest. The adaptive-optics
system uses the star as a source by which astronomers monitor and
correct for the distortions produced by earth’s atmosphere.

Employing the laser will allow astronomers to place an artificial
corrective guide star wherever they see fit. To do so, they shine a
narrow sodium laser beam up through the atmosphere. At an altitude
of about 60 miles, the laser beam makes a small amount of sodium gas
glow. The reflected glow from the glowing gas serves as the
artificial guide star for the adaptive-optics system. The laser beam
is too faint to be seen except by observers very close to the
telescope, and the guide star it creates is even fainter. It can’t
be seen with the unaided eye, yet it is bright enough to allow
astronomers to make their adaptive-optics corrections.

The Palomar Observatory currently employs the world’s fastest
astronomical adaptive optics system on its 200-inch Hale Telescope.
It is able to correct for changes in the atmosphere 2,000 times per
second. Astronomers from Caltech, JPL, and Cornell University have
exploited this system to discover brown dwarf companions to stars,
study the weather on a moon of Saturn, and see the shapes of

"This is an important achievement that brings us one step closer to
our goal," says Mitchell Troy, the adaptive optics group lead and
Palomar adaptive optics task manager at the Jet Propulsion
Laboratory. The goal, achieving adaptive-optics correction using the
laser guide star, is expected next year. This will place Palomar in
elite company as just the third observatory worldwide to deploy a
laser guide system. This laser will greatly expand the science
performed at Palomar and pave the way for future projects on
telescopes that have not yet been built.

"This a terrific technical achievement which not only opens up a bold
and exciting scientific future for the venerable 200-inch telescope,
but also demonstrates the next step on a path toward future large
telescopes such as the Thirty Meter Telescope, " says Richard Ellis,
Steele Family Professor of Astronomy and director of the Caltech
Optical Observatories. "The next generation of large telescopes
requires sodium laser guide-star adaptive-optics of the type being
demonstrated at Palomar Observatory," he adds.

Currently in the design phase, the Thirty Meter Telescope (TMT) will
eventually deliver images at visible and infrared wavelengths 12
times sharper than those of the Hubble Space Telescope. The TMT
project is a collaboration between Caltech and the Associated
Universities for Research in Astronomy, the Association of Canadian
Universities for Research in Astronomy, and the University of

The Caltech adaptive optics team is made up of Richard Dekany (team
leader) and Viswa Velur, Rich Goeden, Bob Weber, and Khanh Bui.
Professor Edward Kibblewhite, University of Chicago, built the
Chicago sum-frequency laser used in this project. The JPL Palomar
adaptive optics team includes Mitchell Troy (team leader), Gary
Brack, Steve Guiwits, Dean Palmer, Jennifer Roberts, Fang Shi, Thang
Trinh, Tuan Truong and Kent Wallace. Installation of the laser at
the Hale Telescope was overseen by Andrew Pickles, Robert Thicksten,
and Hal Petrie of Palomar Observatory, and supported by Merle Sweet,
John Henning, and Steve Einer.

The Palomar adaptive optics instrument was built and continues to be
supported by the Jet Propulsion Laboratory as part of a Caltech-JPL

Support for the adaptive-optics research at Caltech’s Palomar
Observatory comes from the Gordon and Betty Moore Foundation, the
Oschin Family Foundation, and the National Science Foundation Center
for Adaptive Optics.

SpaceRef staff editor.