PASADENA, Calif.- Astronomers itch to detect the very faint galaxies
that were created close to the beginning of the universe. Now a
panoramic infrared camera, one with the largest field of view for a
large telescope, has been installed on the Palomar Observatory’s Hale
200-inch telescope. This much-awaited instrument promises to yield
many new insights for deep-space astronomy.

The Palomar Observatory, which is owned and operated by the
California Institute of Technology, has a long tradition as a pioneer
in infrared astronomy, using both ground and space-based telescopes.
The unique feature of the new camera is a $350,000 sensor
manufactured by Rockwell Scientific in Camarillo, California. The
sensor rests inside a camera that has been provided by Cornell
University as part of their collaborative program with Caltech at
Palomar. Caltech’s contribution-the infrared sensor-was made possible
by a $1 million gift generously provided by Sam and Lynda Oschin for
the upgrading of instruments at Palomar.

The new camera is one of many efforts over the years to keep the
Palomar telescopes modernized and relevant. It’s one of the reasons
that scientific research at Palomar has been remarkably productive
since the observatory’s debut in 1948. Just this month, for example,
on October 4, Caltech astronomer Derek Fox detected the afterglow of
a gamma-ray burst just nine minutes after the explosion. Then, three
days later, astronomers announced the discovery of a spherical body
orbiting in the outer reaches of the solar system. Both discoveries
were made using Palomar’s 48-inch Oschin telescope.

The Hale telescope’s newly commissioned digital camera, whose format
is 2048 x 2048 pixels, will bring unprecedented speed to surveying
the heavens for near and distant objects that emit radiation
primarily in the infrared spectral regions. It replaces the
observatory’s current infrared camera, which had a format of only 256
x 256. This gives the 200-inch Hale “a truly extraordinary leap in
capability-a factor of 64 increase in survey speed at a single
stroke,” says Caltech’s Richard Ellis, the director of Caltech
optical observatories and the Steele Family Professor of Astronomy.

Infrared radiation is not visible to the human eye but offers key
diagnostic features for astronomers. As the universe expands, distant
galaxies are moving away from us. Accordingly, much of the visible
light they emit is “redshifted” into the infrared part of the
spectrum by the time it reaches astronomers’ telescopes. That’s why a
survey capability for locating faint infrared sources is so important
to astronomers. Once astronomers have charted the locations of the
most distant galaxies with such infrared surveys, those galaxies are
scrutinized in more detail with the 10-meter Keck telescope in
Hawaii, says Ellis. (The Keck Observatory is jointly operated by
Caltech, the University of California, and NASA.)

Closer to Earth, the camera will be equally valuable to astronomers
interested in probing solar system sources beyond the orbit of Pluto,
as well as the poorly understood brown dwarfs. The latter are objects
sized somewhere between a giant planet and a star that, due to their
low mass and coolness (2,000 degrees or less), are difficult to
detect except at infrared frequencies.

Each pixel of Rockwell’s camera has a surface layer composed of
mercury, cadmium, and telluride, the compound used for infrared
sensing. Another key element of the camera is its complementary metal
oxide semiconductor (CMOS), which precisely reads the infrared light
from each pixel and converts it to a usable signal. Electronics
developed jointly by Caltech and Cornell staff downloads this signal
and assembles a digital image on a computer.

For several months, Roger Smith, head of detector development at
Caltech, and colleagues, had the use of a so-called
“engineering-grade” camera to “play with,” as Ellis puts it. That
allowed the Caltech engineers to ensure it worked properly, to tune
up the voltages, and to practice its proper installation. Then, last
month, with some trepidation, they successfully installed the
delicate and expensive science-grade version in the camera system
built by Cornell.

Using the 200-inch Hale, the “first light” images were taken by
Ellis; Smith; Keith Taylor, the associate director for development of
the Caltech Optical Observatories; and colleagues from Cornell led by
Professor Steve Eikenberry. The images, reduced by Caltech grad
student Kevin Bundy and Chris Conselice, a postdoctoral scholar,
demonstrate the dramatic leap in imaging capability: with the new
camera, a single exposure of NGC 891 (a nearby star-forming spiral
galaxy) is all that’s needed to capture an entire galaxy. That
contrasts with the previous camera, where a sequence of dozens of
independent exposures would have been necessary to achieve the same
goal. In the coming weeks, a series of Caltech, JPL, and Cornell
observers will be putting the new instrument through its paces.

When Palomar Observatory was dedicated in the summer of 1948, the
Caltech facility instantly became the preeminent astronomical
observatory in the world. For decades, its 200-inch telescope, named
after famed astronomer George Ellery Hale, maintained its distinction
as the world’s leading astronomical instrument. Now, the addition of
the jointly produced Cornell-Caltech camera funded in part by Sam and
Lynda Oschin, says Ellis, “demonstrates Caltech’s commitment to
giving a new lease on life to the 200-inch through innovative
state-of-the-art instruments.”

Note to Editors/Reporters: A photo of NGC 891 is available, showing
the increased field-of-view. Please contact Mark Wheeler. Thanks.

Contact: Mark Wheeler
(626) 395-8733
wheel@caltech.edu

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